One thing to point out is that GAB got the way it is mostly because of the very actors that you describe (in general not these specific people).
Now before i continue I want to say, GAB is, at the moment, and for most of its history, very right wing. ITs content is significantly disgusting and I dont follow even a single GAB person (though have met some nice GAB refugees). So with that said let me continue.
The original mission, and even their current mission, was never to favor right-wing in any sense. They opened in response to FB and twitters censorship with only one goal in mind: free speech. Granted they took this goal to the utmost extreme, but in and of itself nothing horrific about the networks intentions.
However the left, particularly in europe, sees "free speech" as a sort of trigger word to mean "evil things are condoned here". So as a result the left boycotted the system from very early on. The end result is that hte left and even many moderates created the vile nature of GAB simply by boycotting it, leaving only the vile people to remain. Evil thrives in the darkness, by withdrawing and allowing an echo chamber to exist it ultimately snowballed and created a safe haven for that very darkness.
Federation I saw as an oppertunity to bring isolated, cruel people back into a larger community where their views can be challenged for the vile nature they are and hopefully well meaning people could bring some of these people back to the light. But instead the idea of blocking the whole network has only strengthened their resolve and given them an echo chamber where their ideas of prejudism are praised and reinforced.
We have to recognize that while they are entierly accountable for their own actions, we live in a society and int he long run it does more harm than good to silo them away in their own corner of the internet.