It just makes you more connected to the Earth. Like being a living being on Earth under Earth rules. It's called "earth essence" for a reason.

It makes you feel more honest and connected to the truth on Earth. That sometimes you do need to be a little bit rude / terse in order to get your feeling across to the other person instead of hiding behind some fake mask facade like you would when sober; though that makes the weed sound a lot more influential than it is.

If you're not being fully honest with your feelings with another person, you're shitting on yourself. Weed helps you realise that by making you realise that yes, you are an animal, you are of Earth, you are subject to the same rules and laws of Earth; it's natural and normal to be a little bit forceful and naturally honest about how certain people might make you feel, and that yeah, sometimes you can be an asshole, and that yeah, maybe sometimes that's necessary and normal and a part of life. Just so long as you don't make it personal.

So I can see from my experience with weed how that might make a person seem like an asshole to someone else. E.g.:
>Person A smokes weed.
>Person B has left the dishes out -- AGAIN despite being asked repeatedly to not do that.
>Person A confronts Person B about this issue and this times makes sure they understand how Person B's behaviour makes Person A feel, particularly when they've been asked before.
>Person B considers Person A to be an asshole about this, notices they're under the influence of cannabis, hmm! The pot must make them an asshole!

Weed also makes you more insightful and introspective, this sometimes can mean that you over-analyze certain interactions between people and yourself, perhaps unnecessarily, with an emphasis on SELF.
Despite all that, lot of it though depends on the strain, the person, the state the person is in, how often they use weed, the strength of the weed, etc.
If if makes you evil then you probably had some inclination to be so anyway.