As a guest, though, if a host is actively weeding out people because they speak out about being scammed by shitty not-as-described slumlord empty-ikea-box listings, then I probably don't want to give that host money anyway.
I totally agree. To clarify I'm a very active guest as well, so I'm well aware of mis-represented listings. I simply use this as another data point when evaluating a guest.
I don't need to know, because I automatically benefit from not having my trip ruined by staying there.
A lot of people don't seem to get that you can be honest about a booking without sounding like a complete asshole (despite how much I like to complain on HN, I promise that I don't write reviews the same way ^^).
You can say a lot of honest things like "if you expect to cook, be aware that you'll need to provide your own X/Y/Z" or "The wifi didn't work for me" or "I found the bed to be uncomfortably soft" or "It's obvious that nobody has ever lived here because so many basic things are lacking". And if any host would choose to deny you based on those, then I wouldn't want to give them money.
Possible reasons for a host to deny a booking:
1) The apartment is actually unavailable. It happens sometimes. I'm not going to cry about it.
2) The host is scared that I'm going to call them out for lying in their listing. If the listing is a lie, then I don't want to stay there. If the listing isn't a lie, then a good host won't be scared by honest reviews about misleading listings.
3) The host doesn't like my face. It's unlikely but possible. Again, I don't want to give money to a person who makes judgements like that.
I've never had any difficulty finding places while staying honest. Honesty doesn't reduce the number of good hosts available. Dishonesty does increase the number of bad hosts available. I do sometimes suffer because other people were dishonest in their reviews, and it upsets me.