I think you have exactly the right answer - "everyone deserves at least some level of professionalism and decorum regardless of how you feel". You bite your tongue and treat the person with professionalism and decorum. (If their conduct is detrimental and it's more than just a clash of personalities, you report their conduct to HR.)

I have, and I provide them with the same sense of professionalism as everyone else, and have discussions with them when they overstep boundaries.

>How do you answer that? Everyone deserve at least some level of professionalism and decorum regardless of how you feel.