Here's one of my least favorite evergreen internet donnybrooks:
Person A: So-and-so isn't a real Christian [or insert identity here]. Real Christians care about the poor/don't commit adultery/aren't racist [or insert other "good" qualities here].
Person B: I've got bad news for you: lots of real Christians are greedy/adulterous/racist etc.. Stop trying to bowdlerize the reputation of Christianity by pretending the bad parts don't exist!
The reason I hate this is that both "sides" are not just attempting to do wholly salutary things, but they often know the salutary point the other side is trying to make and just pretend not to.
Person B is certainly right in trying to check against an illicit cleansing of Christianity's moral reputation. There are lots of people who are and are recognized as Christians who do bad things, and one can't wave that history away by playing games with definitions.
But Person A is also right in that the public meaning and understanding of Christianity is a perpetually contested concept, and it is a good thing when people try to align that concept with other good qualities. It is good when people who are Christian understand that identity to encompass good things. It is a constant push-pull struggle, and Person A is fighting the good fight in trying to push "Christianity" in a positive direction.
So yes, it would be bad if we just collectively glaze over the bad attributes of various identity/ideologies in a misplaced desire to define ourselves into innocence. But it would also be bad if we sabotaged efforts to present alternative and more salubrious accounts of these identities by acting as if they're forms of cheating.
In theory, a bit of nuance lets these positions coexist. One important lodestone I'd turn to here is Richard Rorty's maxim that "there is nothing deep down inside us what we have put there ourselves." The inherent nature of Christianity (or again, fill in your favored blank) is not homophobia, nor is it LGBT-inclusion. There's nothing deep down inside the concept save what we put there ourselves. If we put in homophobia, then its homophobic. If we take out homophobia and replace it with LGBT inclusion, then its LGBT inclusive. It is not definitionally wrong when people put in homophobia, nor is it cheating when people try to take out homophobia.
In the field, I think a good rule of thumb is to ask what the speaker is reacting to. If someone is criticizing Donald Trump by saying he's "a bad Christian", I'm not convinced it's helpful to swoop in and say "actually, Christians can be bad." If someone is criticizing Donald Trump for imposing Christian nationalism upon the population, I'm not convinced it's helpful to swoop in and say "what he's doing isn't really 'Christian' at all."
Likewise, I don't have a lot of patience for people who try to deny the real strands of homophobia in Christianity by simply saying "that's not real Christianity". That is, to borrow from Bonhoeffer, "cheap grace"; it takes work to excise those strands, it's not something that can be accomplished by proclamation alone. But I also don't have much patience for people who pooh-pooh the notion of doing that work at all because they insist homophobia is inherent to Christianity and anyone who tries to dislodge that attribute is lying -- and importantly, standing up and presenting a different vision of Christianity is an important form of doing the work. Indeed, there aren't many other ways.