People have complained about the message board forever, but the specific criticisms are different now.
In the old days, it was about how there aren't any more great training threads, too many non-running threads, people being too mean and scaring away the (running) celebrity posters. Now, the dominant criticisms are about racism, sexism, facism, etc.
I have to say, I don't see it. Sure, there are sexist or racist things posted, both now and back in the day. But it's certainly not pervasive, and it's not even clear how much of it is earnest vs. trolling. It strikes me that it's no more than you would expect on a large platform with anonymous users from around the world. Most people on LR seem to be pretty decent.
It seems to me that there are only two ways you can make the case for LR being a cesspool of racism and sexism.
First, you can take the position that ANY amount of overt sexism or racism is so utterly unacceptable on a message board that it simply must be removed within minutes. That seems unreasonable. In my experience the complaint based system works pretty well, and the moderators are responsive.
Second, you can define racism or sexism in extremely broad terms, such as someone expressing opposition to affirmative action. But even if you think that such views are racist, at the very least they aren't so OVERTLY racist that it would be fair to judge any forum where such views are expressed as a cesspool.