How you died on Nefarian

[mascaron]

However, I don't see any possible explanation for him calling me a clicker other than to be an asshat about it.

a friendly jibe, joking that you're a clicker, indicating he thinks you're a good enough player that if you had it key binded you would obviously have the reaction time to immediately get out of the stun and lay on hands / bubble yourself and prevent the death.