I've heard a lot about Antifa being a violent group, after reading some of the posts here I checked out some of the relavant info, e.g. with the stats the ADL collates. Here is some data:
Right wing extremists have killed hundreds of US citizens in the last decade. There is no record of a single homicide linked to any Antifa activists.
Antifa doesn't appear to be a group as such, more like a loose association of groups and individuals.
Those elements that coordinate in some way generally do so in response to some other event they want to protest or disrupt, generally reactive rather than proactive.
Sure there are some nuts involved but overall they are far less violent than groups at the opposite end of the political spectrum. Which indicates that the senators involved are so emotionally invested in their own narrative that they can't think straight, or they have some other political reason for this stunt.