Was management involved at any point before the arrest?
Because it just seems like security was doing what they regularly do when facing something they don't now how to deal with. Interfere until people with real badges show up, at which point arrest is almost automatic.
Some important context: these two were arrested for attempting to supply the missing video censored from the exhibit after Republican pressure: David Wojnarowicz work "Fire in my belly." The video featured ants crawling on a crucifix.