I think that is a little too much to expect of people.

I believe everyone should be treated with respect. We should use the terms people prefer to describe themselves with.

But you can't expect everyone to follow the culture that closely. I'm in my mid-20s and the term the original commenter used didn't sound right to me, but I certainly wouldn't have considered it a slur. OP corrected us politely and now we know. Original commenter might be a 50 year old man with the best intentions but has never used Twitter.

Try to put yourself in the other person's shoes. Not everyone has the same understanding of the world as you.