I'm actually going to buck the trend and say the masks are acceptable for two reasons. First of all, these guys are people. They don't want to be doxxed by some nuts on reddit. Secondly, some of these guys would want to work undercover at some point. It isn't going to take too much effort to have an AI program do facial recognition on news clips as these guys arrest folks and compare it to that new connect that wants to sell me a bunch of drugs a few years from now. I could probably do it and I'm not that good.
I do think they should be in uniform and there should be some way to identify them such as a name tag or even a number that can be traced back if necessary. I certainly don't like the look of vigilantes arresting people as a matter of course because some agents don't want to wear a uniform. It makes these things look less like a professional law enforcement operation and more like a bunch of bounty hunters.
I don't blame these guys for doing what the elected bosses order them to do. We don't want them to have no accountability and do whatever the heck they want. But I do think they should do the arrests as humanely and professionally as possible.