Suppose there was an interesting conference being held in South Dakota. Would you go? There is some precedence—I knew some computer scientists who refused to attend meetings in South Carolina a few years ago when they flew the Confederate flag over their State House.
By avoiding the conference you are mostly hurting the researchers in that state, who likely do not share the government's viewpoints and cannot easily move. Many scientists worldwide don't like much of current US foreign policy but I would hope they wouldn't avoid American conferences for that reason.