I need to ask you not to call me brainless

Let me start by saying I’m not a very confrontational person. I’m not good at thinking on my feet, and don’t defend myself well verbally. If I do find myself in a position where I need to force an issue, I am extremely uncomfortable. So it makes me nervous to engage others in face to face political banter unless I know the person very well. Because I can’t get upset at work (I have a job to do) I tend to ignore the political talk I hear there.
I am not a supporter of Trump, but I work with a very vocal supporter of Trump. It is difficult to listen to at times, because I find myself wanting so badly to insert my thoughts. Usually I don’t, because the backlash from my coworker is so swift and at such a fevered pitch that a second response from me or even a clarification, is often impossible. Occasionally something so fully incorrect or insensitive is said that I feel I must say something. And tonight I felt I couldn’t let it lie. Speaking to another coworker about the election, my coworker who I’ll call Marc, said, “At this point, anyone who votes for Hilary has to be completely and utterly brainless.” Here is the conversation that followed five minutes later in the adjacent room.

“I need to ask you to not call me brainless.” I say.
“What- did I call you brainless?” He says.
“What you said to James? About people voting for Hillary.”
“I didn’t mean you!”
I give him a look.
“You shouldn’t take it personal. (Continues with me, walking into the room I’m also walking into) You should hear the stuff the other side says though.”
“I don’t say those things.” I say quietly.
“Ok, well. I apologize.”
“Thank you. I appreciate that.”
And a few minutes later.
“You know about before, I’m sorry. I won’t do it again. I just get so passionate about this stuff.”
“I know. Rhetoric seems to be getting out of hand everywhere.” I say.
“It’s the election. It’ll be over soon though, alright?”
This guy and I disagree pretty fundamentally on a very lot of things. But otherwise we get along. I don’t find him to be a person that knowingly harms people. I called him out on a personal insult and he stepped back and apologized. I feel angry enough sometimes at Trump voters to call names, but I don’t. I’d like to think that if I fell to personally denigrating others, I’d back off when someone called me out. It’s going to be really important this year to remember that the US is populated by other human beings. We are going to vote as human beings and accept the results as human beings and live together the next four years as human beings. I implore you to remember to treat others as human beings in your words and actions. By all means rail against injustice, despicable policies, or the words of the opposite candidate that you find thoroughly distasteful. Do not call the human beings in your life brainless, asshole, deplorables simply for the way they are voting. We are better than that.