People need to grow up when discussing things like transphobia. People make it so unreasonably difficult to discuss it due to their own made-up definitions.
You do not have to be transphobic to engage in behaviour that can be seen as transphobic. This isn't some revolutionary idea, it's a basic fact. You can say something racist and somebody will say "hey that's kinda racist", yeah? That's a thing. There is such thing as unintentionally offending someone. You don't need to put up some iron wall of "I'm not transphobic tho" when someone is trying to explain that perhaps it isn't a good idea to generalise an entire group of people. Sometimes you'll unintentionally engage in "phobic" behaviour, even the greatest saints can unintentionally hurt someone. Everyone makes mistakes. The worst thing you can do when your behaviour is pointed out as problematic is turn it into a personal attack. This can apply to any social situation for any time where you say something stupid. "Hey what you said there is kinda bad" isn't the same as "Hey you're a douchebag".
And no, transphobia - and any "phobia" referring to a group of people - does not refer to an irrational fear of them. This is an anti-LGBT trope that's been peddled by TERFs and other cliques for years. Homophobia, the first "LGBTphobia", was coined in the 1960s based on the greek word phobos. This word means anything from morbid fear to simple aversion. Getting hung up on something so utterly stupid, just to look like some pseudointellectual to a concerned friend, says a lot about the person doing it. The word is a way of conceptualising a pattern of aversion and prejudice towards a group of people. A pattern of behaviour needs a word to help explain it, this goes for things like narcissism. Without those kinds of words, it is difficult to socially advance. Again, this isn't some revolutionary take, it's something that has been done for centuries and is the heart of sociology and psychology as subjects.
I don't know how common this is outside of the UK - it's called TERF Island for a reason - but good fucking god this behaviour is so ridiculously obnoxious that I don't even want to entertain it anymore. I obviously will, my existence hinges on it, but to say it demotivates me is an understatement.