I'm sure there are many gay people who like the pp are broadly supportive of the idea of Palestinian political autonomy, or object to the current military actions against them, while being very aware of and disapproving of their position on homosexuality.
However, when I've seen people at these marches interviewed, they seem to believe in the "all minorities/oppressed people are on the same page" type of thinking. They truly don't understand, for example, when non-white people are Tories, as they believe that "non-racist" is an inherent characteristic of the left, and "racist" is a characteristic of the right - as in, right wing people decide to be right wing because it is racist and they agree with that.