1-Yes I do. I'm an overthinker who usually wastes way too much time, effort, and energy on thinking about which EXACT words I want to use in a given situation and at some point I just decided that using they/them works perfectly well most of the time

2-For example, I never said "always", I said "the majority of people" which is just anything more than precisely 50%.

3-If I'm being real picky, the MOST commonly used pronoun I say is probably the variations of "you". If I were to apply it to this situation I might tell you "Gee, someone must have pissed in your cereal this morning". But if I was describing this interaction to a friend I would tell them "This one person was really pissing me off, someone must have pissed in their cereal this morning." I don't know you or how you identify or what pronouns you prefer but it is still perfectly valid English grammar. See how that works?

4-Stop white knighting for people who are perfectly capable of standing up for themselves, at least not over stupid shit like this. It will never make them more accepted by bigots (your ACTUAL opponent). In fact, it only makes their acceptance by the rest of society that much harder if they feel like they have to walk on eggshells every time they try to have a conversation. If you see something truly, unmistakably transphobic, go right ahead, I won't stop you from trying to stamp that shit out. But trying to gatekeep people who 'aren't the right kind of Ally' will earn you no friends, not even from the community you think you're helping

I do it when I'm unsure how someone identifies.