"Intention, I tell you, is kamma. Intending, one does kamma by way of body, speech, & intellect."
- http://www.accesstoinsight.org/tipitaka ... tml#part-5
Any negative mind state and thoughts creates kamma. But don't be so anxious that you create undue suffering for yourself. Is it serious bad kamma? Probably not. Shit happens and some people are
idiots. Use it as incentive to try and change. Just try working on your mindfulness, step by step, slowly you'll find you'll get more control over your mind states and find that you don't want
to be angry at someone, because it causes yourself pain. Then gradually you'll let go of such things, and start focussing on generating positive states of mind. Do you regularly practice metta also? If not that's another thing that might help.
Sorry that's probably not very helpful, I'm sure others will have better things to say.
"For a disciple who has conviction in the Teacher's message & lives to penetrate it, what accords with the Dhamma is this:
'The Blessed One is the Teacher, I am a disciple. He is the one who knows, not I." -