You know what? I think it's fine when people who have been lucky enough to not have been oppressed or threatened by less-than-blatant language don't immediately recognize it. They hadn't grown up with it, faced it on a regular basis, acquired the context to pick it up 100% of the time.
But when the people who DO recognize it and try to point it out, DON'T FUCKING DISMISS THEM AS IF THEY DON'T KNOW WHAT THEY'RE TALKING ABOUT. That's where I draw the line between "I wish they understood it" and "fuck 'em."
You've got less experience and context facing and living it, don't think that you've got the same level of experience and expertise as the people who are made unconformable or threatened.
Not all racists and transphobes are going to make them obviously racist and transphobic to straight white people. Just enough to scare off minorities and promote themselves to the like-minded and easily-influenced. Look out for more than just people saying the n word, christ, it's not that complicated.