Because they don’t care about the rules, but they know the other side does. Whenever they act, they defend not their actions, but the process by which they were allowed to do them. If fascists break the rules, liberals can only request that the rules be followed. If they follow the rules, put on a tie and speak like an academic, liberals can only trust that their ideas will be voted against. In either case, they don’t know how to call a fascist a fascist, and they don’t know how to fight fascism within the current ruleset, and they never will.
Yes, beset by a mountain of conflicting interests and decades of infighting and ideological purity testing. Most Democrats are terrified of taking stances on wedge issues because any stance they take could break up a coalition that has all the durability of a Faberge egg. Republicans either don’t have this problem, or they don’t have it as bad. Despite having as many if not more factions than the Left, they all value loyalty and in-group cohesion, which allows them to come together every 4 years to form a unified voting bloc.