Is it considered forbidden hypocrisy in Islam to be courteous to people whom I cannot bear to sit with due to actions or characteristics they display?

What you are doing is a form of conciliation (mudaraat), not hypocrisy (nifaq). We advise you to offer them sincere counsel (munasaha), pray for them, alert them to their mistakes, and give them gifts, based on the Almighty's saying: ﴿Repel evil with what is best. We are most knowing of what they describe.﴾ and ﴿Repel evil with that which is best, and behold, he between whom and you was enmity will become as though he were a devoted friend.﴾ And based on the Prophet's (peace be upon him) saying: "Give gifts to one another, and you will love one another," and "Give gifts, for indeed gifts remove rancor from the chest" or "remove ill feelings." You can also give them messages that make them aware of the ugliness of their actions, for a believer offers sincere counsel to his people.