Thanks for the links. After reading the reports, it is clear to me that the officers used excessive force. On the first page of the taser use policy, it says the officers should consider these factors before using the taser:
(a) The potential for injury to the officer(s) or others if the technique is not used,
(b) The potential risk of serious injury to the individual being controlled,
(c) The degree to which the pain compliance technique may be controlled in application according to the level of resistance,
(d) The nature of the offense involved,
(e) The level of resistance of the individual(s) involved,
(f) The need for prompt resolution of the situation,
(g) If time permits (e.g. passive demonstrators), other reasonable alternatives.
I think they used it in consideration of (f). If they didn't get him out of there quickly, there was the possibility of a some sort of student demonstration breaking out.
But - the guy was demonstrating passively, so, under (g), there was time to just put the guy in handcuffs and drag the guy out. Then you just post an officer at the library to check campus IDs for the rest of the night. Add to that the fact that he disclosed a medical condition, bringing (b) into the equation, and I think it's clear that they used excessive force.
There really was no need to use the taser in this situation as there were reasonable alternatives to doing so, and there was potential for serious harm to the protester.