Over the years, I've heard/read some, including retired and active duty military, say things like they won't follow unconstitutional or illegal orders, but I think that's being naive to how people behave in the context of institutions and their power dynamics. Humans are social creatures. We're group conformists by nature, and since we moved out of the prairies and forests and into cities over these last 10,000 or so years, we've adapted in ways that incline us to operate within the power frameworks that form the basis of civilization.
In short, we're engineered to obey authority. I mean, sure, there are limits. It was soldiers who risked court martial to speak out against the massacres of Mai Lai and there were similar episodes in more recent conflicts, but generally speaking, we're creatures that do what the group does, and we give authority a lot of slack in many cases until we know that something is just way out of bounds.
Trump will say that he wants those protesters neutralized so that ICE can do its job. The Guard will impose a curfew if that doesn't happen. Hopefully, it doesn't go much beyond that, but it could.