There's a difference between assuming something about someone based off something that's part of their identity and refusing to acknowledge their identity at all. Especially not because it's harder and you might make mistakes sometimes.I like to deal with people as individuals, not political identities, because I feel political identities are completely irrelevant.
I don't want to be considerate of your religion, gender, race or whatever "groupness" a person might feel the need to identify with.
For example, say you're a Christian. What does that actually say about you? Nothing, absolutely nothing. Does it make you a good person, a bad person? Does it make you trustworthy? Does it make you smarter or less smart.
The only thing it might do is if I held any biases or prejudice. I might judge you based on something that has nothing to do with you.
So I have to worry about offending you based on something that has nothing to do with you as an individual.