So, you make an impression based on outward appearance. In what way does biology determine that?
I refer to them with biological terms.
No, you're not. You're referring to them with a gendered term.
I've always refered to their biology, back when they were used as the same
They weren't. For as long as gender has been understood as a social construct, it has been distinct from biological categorization.
this was not a problem, but now that they have redefined gender to mean something other than biology,
Gender never meant biology. For as long as the word gender has been applied to humans, it has been a distinct, social category to biology.
people like you have a problem with it. But I will continue to refer to biology.
No, you're just deliberately misgendering people because it upsets them. That is literally the only reason to do it, rather than using gender as a social construct like literally everyone else, and how it has ALWAYS applied since the terms has been applied to people.
It's just pointless cruelty.
He/She are biological categories.
No, they're gendered terms. For as long as you have been alive, this has been understood. You know that when you refer to human men and women you are referring to something that is very different than simple biology, and you can't possibly claim otherwise. If you did, it would mean that you personally investigate the biological makeup of every individual you ever refer to with gendered terms, rather than making loose associations based around a set of socially-formed expectations. You would never have referred to anyone as "manly" or "womanly" or "lady-like" or "boy-ish". You use the terms in a social context, just like literally everyone does. You just make one exception for trans people. And the only reason to do that is because you know it upsets and harms them.
Why not just use their preferred gender and pronouns? It is literally effortless, harmless, and makes the world a better, nicer place.
This applies to all mammals; not just humans; this is an undeniable fact.
If you think the useage and definitions of pronouns and terminology (or literally any words) are "undeniable facts" then you don't understand how language works.