Most people don't have traumatic experiences and other things. I'm just answering people discussing me and my opinions on a message board. I'm trying to be polite actually

, but yes- I'm not giving someone the benefit of the doubt that they will have a panic attack if a stranger asks to sit with them. Will I incorrectly assume that someone is ignorant/selfish? I'm sure it has happened, but most of the time I'm willing to bet I'm right.
The first person to call out my post on this thread said they don't like sitting with strangers because they don't like to share, they don't want to hear about their lives, blah, blah, blah. And I said I think that's selfish.
Everyone else came on here and started giving examples of that instances where someone would say no - but those are outlier instances.
My original stance stands - if you say no when someone is asking to share when there is nowhere else for them so sit, I will assume you are ignorant to the fact that there is no more seating. People took offense to my use of the word ignorant.
So I said if you don't want people sitting with you because you "don't like to share", don't want to make small talk", "shy" - then I think that's selfish. It's your right to say no for those reasons, but I can still have the opinion that they are selfish reasons.