Hmm, that's unfortunate. Do you two share a lease or is one of you subleasing to the other? In a subleasing situation, sometimes the person who is subleasing really hates living with other people (especially you!) but magnanimously put up with it because they are cheap bastards living outside their means. This happens a lot in DC btw, sometimes I read the ads and I'm like geez, am I allowed to breath in your space or is that against 'the rules' too???
Frankly, there are lots of uppity assholes in DC with chips on their shoulders. I know, I hate. But only because I care.
If you are the one subleasing to him, it's easy to put him back in place and just bring up things that are annoying you. After all, you're technically his landlord.
I think with two introverts, or people who don't really 'talk things out' things can get really tense or unpleasant like this. Are you sure he is INFJ? It's possible he is just a moody so and so and not really aware of how he is coming off. Some people are just kinda rough around the edges or otherwise not really good with social nice-ities. Some people are just really moody and give off vibes they aren't aware of or 'able' to control. Instead of being self-contained with their angst or pain, they are like weeping sores of negative emotional energy. And cattiness. Not fun for innocent bystanders around them.
I've lived with people like this -- we were otherwise friends so it was easier to weather, but it can be a total drag to live with moody people. Especially if you have crazy Ne and Fi. And especially when their personalities flip or they act out.
Question: is it his 'negative energy' you have issue with, or do you think he's acting out, being catty, basically being disrespectful?
Absorbing what you perceive as 'negative shit' is a really bad idea. I've done this before, but moreover, have just let things fester in the air intsead of naming it. Generally, when people hold things in re: a roommate situation, by the time things come out, the dam's basically burst and then you just have all out war.
For me, I can get pretty emtional or upset when I feel sleighted for no reason and it's very unhealthy to keep it in. When I get mad or have a concern, I find it's best to sort out the actual issues and what points I want to get across and what I want from the other person before I talk to them. And when I confront the person with my concerns, it helps keep me focused on what my issues are instead of getting sidelined with emotion.
Or rather, it helps me focus my emotion but keep my delivery more neutral and matter of fact so the other person has a chance to really hear what I'm saying in a non-defensive manner. This is the best way for resolution and not for fighing.
Sometimes though, let's face it, we just want to fight and have a good screaming match and tell that so-and-so exactly what we think of them. There is no 'desired outcome' other than letting off steam.
Or tactic 2#
In your situation also, perhaps your roommate is not doing things intentionally to make you feel bad. Do you believe some people are just assholes and cannot help themselves? Or that they are well meaning but will just rub you the wrong way and that's their god given purpose on earth? Can you find compassion for them in your INTP heart? Can you just see it for what it is and just brush it off? No one's saying you have to hug it out with him, just that if you change your POV it may not bother you.
Basically, I don't think you necessarily have to revert to being nasty (being firm maybe) to get him to be more aware of his behavior, or if he's more aware of it, to change his behavior.
How have you been nasty to him in the past? What have you brought up to make him behave better?
BTW, I've lived with 20 roommates over the years in the DC area (yeah I get around) so I speak from experience.