It’s not difficult to define.
It’s about people’s choices.

People can choose to own a gun, choose to want to own a gun, choose to own a whole armoury.
I think owning a gun is stupid. I live in a country that successfully regulates guns.
Saying “I think gun owners are stupid” isn’t hate speech because they have chosen to own a gun.
If I said “gun owners should use their guns in themselves” that becomes hate speech because it’s wishing harm on them.

People choose to be Republicans, trumps choices in life are why he is where he is.
Hate trump because of what he does, not because he has blonde hair.

People don’t choose to be gay, or be trans, or be Jewish, or be black, or be short or whatever.
Which is another way opinions can become hate speech.
If I said “I think gun owners are stupid” that isn’t hate speech.
If I said “I think black people are stupid” that becomes hate speech because it is grouping people by something they have no control over.