He did plead guilty and paid a fine, because pulling the alarm is a crime. I’m not being alarmist, activating the fire alarm costs real money, draws the attention of fire fighters, wastes the time of everyone in the building that must evacuate, and reduces the likelihood that anyone will take the next alarm seriously. It’s not a felony, but it’s not harmless.
It’s a crime when kids do it, too, but usually they don’t prosecute it. However, this is a Congressional Representative. Whether we do or not, we should expect more from our elected officials than we expect of school children.
I also think you’re putting too much weight into a censure. It has all the teeth of a strongly worded email sent to an unmonitored inbox. You’re correct that it is the strongest form of condemnation, and I do think the GOP is abusing the censure, but I don’t have a problem with Congress formally disapproving of an adult member of Congress pulling the fire alarm. It wasn’t an aide or a teenager on a school trip or a confused septuagenarian Senator.
The other censures are pure theater, and the more censures they hand out, the less anyone will care.