Is this one of the 'actually controversial' issues you were pleading to discuss a few posts ago?
Whether they were invited, showed up on their own, mutually agreed, or were Shanghaied, does it make any difference? But you raise a good point- they were pretty clearly welcome. I wonder if Coulter and others denounced the combative contingent on their own side, if that would have an effect. I have argued that these groups are in this by mutual consent, as opposed to one attacking and one defending. Antifa have been initiating conflict at the events by their presence, but it has been shown (esp OC) that the pro-Trump crowd sometimes initiates actual violence.
It is a chicken-and-egg problem regarding who started hostilities, as antifa goes back to protesting fascists for years, and neos being accepted into a mainstream party-in-power (shudder) is a new development. A lot of people may see antifa as coming out of the blue to attack Americans, while antifa might say they are continuing a long-running fight against fascists who only recently been welcomed into the mainstream.