I'll propose that there is a reason for this. The tactics of the Social Justice movement is to demonize people who disagree with you and attempt to get them fired or ostracized from society. The tactic is to find the most extreme version of that opinion and try to make that the model for the whole group, even though the center of it might be more moderate. For example, there are a lot of people that have been concerned about the amount of immigration to the US for years and any attempt to restrict immigration was called racists. It's easy to do since there will be extreme racists that also support restricting immigration. You just need to interview one of the clear racists and make them the poster child for the whole group. I saw tons of the meme with Pepe the frog from the alt-right and never saw a single one that was racists. When it went mainstream, someone found out that racists were using it too, so they attached the racist label to the whole thing and tried to get any discussion from the alt-right tied directly to racism and Nazism. There are racists in the group for sure, but I heard a lot of other parts of it as well.
This is the same reason I was so opposed to the witch hunt of punishing everyone associated with Peter Thiel. Trying to get someone fired for their political beliefs sends the middle people underground. They are fearful, and their whole lives are not centered around their political identity, so they just stop talking about it.
The result is that the only people willing to talk about these things are the extremes, or the weird or the people who really take "I don't care what you think of me" to the extreme. This is why Milo Yiannopoulos is the spokesman for these ideas to people. He is the only one willing to talk publicly. He is an extreme, and deeply flawed person, but he is willing to say things no one else is, so he has a following. Trump is also a version of this. Lots of his supporters are more reasonable than him, but they got shouted out of the public discourse and were call racists anyway, so that only left the extremes left to represent the center.
I think there are lots "worthy opponents" out there, but if they said they support less immigration, they would be called racists and everything they ever said would be quote-mined until something unacceptable was found and they would be run out of the public space.