Shared blocklists are a pain. If you at one point happened to make a bad but well-intentioned pun, you ended up[1] on a blocklist meant for blocking fascists[2].
1) Some political views correspond strongly with problematic behaviour that a conference would rather not deal with.
2) Virtue signaling for PR purposes.
This is kind of like considering an "anonymous" donation more deserving of praise than a public one.
2) Probably because consent can be enforced this way much easier than it can be created in a real discourse. Especially in Germany it is frowned up by leftists to even talk with people from the right-wing spectrum.
I get (1), but (2) makes me wonder whether we learned anything from history at all.
I also know of 2 larger conferences in Europe where accounts were monitored and if activity indicates the person is present, they were removed from the venue by security.
Statistically speaking it should. Do you know if it's proportionally better than just blocking 1 in 10 would-be attendees at random?