Thanks for saving me all that typing. 
ETA: The second time you got in and there was glasses on your seat, you should have tossed them as far as you could. He would understand if you said it was your habit to throw things on your seat as far as you can.
This.
I agree with this, being someone who got a perforated butt sitting on some of mom’s sewing stuff (she had to suddenly drop what she was doing and I didn’t look before I took her seat).
I agree with this because, well, you don’t put your glasses on a fucking chair.
My SO always puts his sunglasses on the passenger seat. Drives me nuts. Not because I can’t be bothered to look before I sit, but because it’s a stupid ass place to keep a delicate, expensive item. I always look before I sit, but after giving them back to him initially, any other times we get out of the car during that same day, he puts them somewhere else. He’s not dumb or egotistic enough to repeat the behavior. At least until the next car ride. 
Another vote for: your friend is an ass. Get rid of him.
Anyone stupid enough to put their glasses on the seat, not let their friend know (did he?) and then get all pissy about it, and say something stupid like,
deserves to have said glasses broken.
Haven’t read others’ responses:
maybe he didn’t have to put it in such dickish terms (that’s a real poor way of making his/her point) and maybe he could’ve been nice and not put them on the seat again, but the ultimate responsibility for not sitting on someone’s shit is on the owner of the ass
some friend! Why weren’t his fabulous $600 glasses on his head? You chould have said ‘your glasses bruised my butt, I can’t sit comfortably and I’m suing you for pain and suffering’.
Next time you drive and bring along your collection of nails sticking out of a board.
I find it very odd that you wouldn’t even check the seat before you sat down. Whenever I’m a passenger, I get to the door, look inside, then move anything before I sit. That said, what you did was perfectly innocent. This friend of yours is an ass, and he’s a self-important ass for doing it twice and refusing to change.
Next time pick up the glasses, tell him to put it on, then punch him in the face
Yup. Here’s the Dutch wiki, which you probably can’t read 
. My own WA (that’s how its’ called) insurance costs me 20 dollars a month, and it will pay for damages up to 1 million dollars. Filing a claim is a huge PITA though, lots of red tape and checks for fraud by the company, but if the OP’s asshole friend hit me with a 600 dollar claim for glasses, yes, that is what that insurance is for.
Here are some random linksin English mentioning this phenomenon.
This thread reminds me of something I witnessed over the course of several months some years ago. My route to work included a narrow street with a sharp left turn at the bottom of a hill. The guy who lived in the house on the outside of the turn would park his truck on the street. The truck got hit a lot - every so often I would see new damage, such as a bent bumper, broken mirror or dented fender.
One day as I was going to work I saw a sign out in the street next to the truck. It said:
I was amused. Apparently this guy would sue everyone who hit his truck. If it were my truck I would park it somewhere else, but he was stubborn and proud of it.
I saw the sign every day. About a week after its first appearance the “2” was crossed out and a “3” was written in. A while later the “3” became a “4.” When a new month started he would put out a new version of the sign with a zero and the counting would begin again.
I thought about sneaking over there at night and replacing the sign with one that read, “Too dumb to park in driveway,” but I didn’t want to get shot.
This continued for several months. One day the situation changed - the truck was parked in the driveway, and the curb where the truck had been parked was red. There was still a sign in the street, but now it read:
Usually when someone hits a parked vehicle it’s a hundred percent the driver’s fault. But in this case the guy kept parking the truck in the same place despite the fact that he knew it wasn’t a safe spot. The city eventually came to the conclusion that the truck owner should have reached long before if he hadn’t been such a stubborn jerk.
I don’t even think the first time was your fault. I would have still probably offered to pay half of the damages in that situation, unless he said “tough luck, you’re up for the full price”, in which case he’d get exactly nothing. What an asshole.
Boy, am I really late to this party.
I cannot tell you how many times my husband has left his glasses in the passenger seat. Most of the time I think to look before I sit, but i’m not prescient, so there are accidents. Hubby has never blamed me for this, not would he blame anyone else in the passenger seat. He’s addle brained, he knows it, and he’s trying to not be so.
So:
OP: not to blame
OP’s friend: needs to get a clue, and not be such an ass
Placed anywhere other than a receptacle purpose-designed solely to receive asses (i.e. a chair), I would agree. Put your shit on a chair, it’s going to get sat on.
Brilliant. Once again, a case I’d love to see on Judge Judy.
I have read the whole thread. Sure, you should look where you park your ass, but you know, I think it’s incumbent on us to remember what things are used for and not put important things in a sitting spot. Because really, the CHAIR is for SITTING. I store things on my passenger seat, too, but it’s still a CHAIR.
Yeah, the liability is more towards 50/50 on the first occurrence, but the second time, complete with bad attitude? Heading into jerk territory. As a longterm, “can’t find my glasses without my glasses” glasses wearer, it is up to ME to make sure my vital glasses don’t get broken. I could put them on the floor on my husband’s side of the bed every night and admonish him to be careful not to step on them, but I don’t, because I’m not stupid.
I would have responded with
“Oh believe me, if I had wanted to smash your glasses I would have done it with my fist… while you were wearing them on your stupid looking face. Now, do you really want to start something with me?”
Your friend is a stupid, conceited douchebag - if you don’t want your expensive stuff to get sat on, don’t put it somewhere where people sit. What an idiot.
Sure it’s always in your best interests to look before you sit, but it’s his responsibility alone to find a safer and more obviously appropriate place for his things, especially since people have a known tendency to not to pay attention to what they’re doing. And his ‘I don’t change my behaviour’ remark shows that he’s not mature enough to sit at the adult table.
Your friend is a douche. I seriously doubt you can un-douche him using logic.
If he ever manages to get married, I predict it will be a short, miserable marriage.