I have seen the comedy line similar to the subject header used in the movies Bridesmaids and Knocked Up, delivered by exasperated women regarding their child and husband, respectively.
The lines are funny partly that they reveal “a woman-sympathetic” fact about a taboo subject.
The thing is, it has never been true in my experience.
I feel in my bones this is a SD question.
Is it just me or is anyone else having trouble parsing this?
It’s not just you.
No, it’s not true in my experience.
Assuming I’m parsing it correctly - if you get semen on a soft towel, will it never wash out to be as soft again?
I don’t know the answer, but the question appears to be “If sperm(semen) gets all over a nice towel, can it be washed and returned to its original fluffiness?”
I assume there is zero reason it couldn’t. Why wouldn’t it be able to?
Don’t towels always lose a bit of their fluffiness after each wash, regardless of how you got them dirty? Any towel washing tips to help them retain that original fluffiness?
I suspect that the original statement is a metaphor for how a relationship loses its luster after sex becomes involved.
Correct. Sorry about the garbled syntax (too excited maybe)?. I agree, I have not found it to be the case, but-- based on two usages of the “fact” – it seems to be some kind of trope. For what I don’t know–women always having to cover for a man/child sexual incontinence?
The metaphor idea is nice, but in one case–and I can see it being said in many sitcoms-- the son is being talked about.
I was always worried about stains on the toilet myself, since you asked. 
Even if this was ever true (& it sounds like utter hogwash to me), there are enzyme-based detergents now, & fabric softeners.
And if you accidentally drop a Viagra capsule in a load of new towels?
You’ll have hard water problems, so use more detergent if you want things to come clean.
Do you need the answer fast?
If your towel is stiff for more than four hours, call your Dry Cleaner.
Are we not the Dope? Commence experimentation!
The answer lies in the thread count.
Perhaps it has to do with the idea that the towel becomes ‘icky’ somehow because of this. For some people that towel will always have that ickyness associated with it and will find fault with it, such as it seems not as soft after washing.
It is also possible that, back in the days of hand washing, someone who had a icky response would wash it extra hard, today perhaps a longer cycle or extra detergent, which would deteriorate the softness.
So it is not the act of ‘sperming’ but the reaction to it that makes the towels less soft.
And this time, no pan and no oven are required…
I believe this is correct.
Also, since we’re on the topic, what about silk as a target of the money shot?
I don’t know anyone who uses silk sheets or PJs. I presume that it is permanently stained from blood emanating from a severed horse head. Perhaps the results would be similar with sperm.
That sure would have made for a different feel to the movie.
I can only vouch for white terrycloth washcloths, but I can attest that since I do laundry every couple of weeks, it has time to “set in”. They do seem to have a different texture afterwards, and often stain them yellow 
“Spermed”?
Verbing weirds language.