Perhaps these bans are happening not because of political affiliation but due to the messages these particular people (e.g., Trump) are espousing.
Parler go banned because it's full of message calling for (e.g.) Mike Pence to be hanged and other such things, and Parler isn't / can't do much about it, and its infrastructure providers (AWS, app stores) do not want any part of it per their ToS.
No one has cut off Mitch McConnell because he hasn't been calling forth angry mobs to storm Congress (or the White House).