you stood your ground and said the truth right? theres nothing wrong with that. obviously this c guy needs help dealing with his own issues, and though it may be a noble task to try and befriend him and put up with him, faking a friendship especially if he is hurting you or those around you is not worth the time. obviously im not saying he is less of a person or anything, but theres only so much you can do, hes not really your responsibility. the best thing would be to encourage him to get more help and maybe talk to his parents (tho idk the exact situation he is in) dont feel bad tho, the best thing i think you can do for someone is be honest, and even though c may not like it, it is his fault for not understanding that friendship is not unconditional.
I don't know if it was the right or wrong thing to do, but if you don't like the guy then you shouldn't pretend to be his friend because he's too sensitive to handle it otherwise. I probably would have done the same in that situation.