Princeton is a private institution, and has a greater ability than state institutions to set its own codes of conduct for its students. That being said, as one who wants Princeton to remain a strong institution, I don't understand what the university's interest is in limiting free speech. Particularly booing at a play. The only exception I might make to this are efforts to make sure that invited speakers or scheduled performances can actually be heard and aren't drowned out by protesters, but I don't get the sense that this is what is going on here.
This "unwanted verbal conduct" standard that a number of universities have adopted is absurd, and is only harming students by releasing them into the real world believing that the government will protect them from encountering any criticism. In this sense, Princeton and other universities are creating students in the modern Islamic mold, teaching them they should somehow be immune to criticism and that they should react with rabid outrage at the first person who says anything negative about them. The only difference is that these students are being taught to respond with lawyers rather than explosive backpacks, but the outcome in terms of stifled free speech is the same.