From my experience in the past they say two things:

1 - attraction is about gender identity. Gay men feel attracted to everyone who identifies as man

2 - attraction is about gender expression. Gay men feel attracted to masculinity

Sometimes they might change from 1 to 2 mid-conversation. Once I was talking to a guy who was very 1, he was all about "trans men identify as men so gay men like them too". Then I showed him a picture of a cis guy who is conventionally attractive and masculine (yet he doesn't identify as man) and asked him if he thought that gay men wouldn't find them attractive, even though they doesn't identify as man. Then suddenly his view changed to 2 and he started saying that the person is masculine and their masculinity is attractive etc.

I like this way of dealing with this topic, pointing out these contradictions. It's also good to keep track of what others are saying, because they love to use the "nobody actually says that" line. So it's good to be able to say "no, actually this and that person said it".

Another interesting line they use is that you can't see someone's genital if you see them on the street and find them attractive. If they're a type 1 you can easily point out that you can't know someone's gender either, so you'd be assuming either way.