I too have similar thoughts and feelings come into my head at different times when I see random people in different circumstances.
As agreed with the OP I do not feel any malice or hate towards these people, and if I did interact with them I would treat them with the respect I treat any stranger I meet with (unless they act in a way that isn’t deserving of respect, even in this situation though I wouldn’t be rude).
I have discussed this my girlfriend on a few occasions and she claims to have the same feelings at different times. We are both extremely similar in our interactions with different people, both of us trying to be as polite and well mannered as possible, to respect and to hopefully leave a positive impression with the person we are dealing with. To me this is trying to be a good person, something I try to do whether I’m feeling happy, sad, annoyed, angry, tired, whatever. If I’m feeling uptight I don’t think its right to be rude to people that have done nothing wrong to me. If this means putting a fake smile on my face and pretending to be happy so the person has a positive experience with myself I will do it, even if its the last thing in the world I want to do.
And this I think, at least for myself, is where the problem described in the OP stems from. As I’ve said I try to be as positive as possible when interacting with any person. and I suppose it annoys the hell out of me when I try to be nice and don’t receive the same treatment back. Situations such as someone scowling when they serve me in a shop, people rudely staring at me (I happen to have quite a few visible piercings (I’m sure my septum ring is the one that bothers most people) and working in a suit and tie office environment I often receive some of the rudest stares off people, sometimes people will not even take the same lift as I do!!), or little things like telling someone to have nice day to have them look at you blankly and say nothing really annoy the F@#K out of me.
All this leads to a predicament in my head. I begin to dislike people because of all the negative experiences I have had with them, yet still love people because I know how good, honest and caring people can be. I think the way my mind deals with this is to indiscriminately put people down in my head, vent if you will at the annoyance I feel towards rude people, yet still continue to be polite and well mannered in all situations I can be.
Do I feel bad for doing this??? NO not at all. My thoughts are my thoughts, my brain is everywhere and often some strange thoughts come up. Some of these would be considered bad, yet I feel that if I don’t act on these thoughts then I have nothing to worry about them.
Therefore I will keep venting at random people in my mind (not that I can really stop it). To me it’s a positive thing. If it keeps me still being able to be happy, friendly and polite to perfect strangers, even ones that don’t deserve it, then it can’t be a bad thing.