Not trying to "flame some more". but maybe you could point out MK's weaknesses to your friends? Like killing over the top of the screen? He lives for forever when people try to KO left-to-right, but over the top he can go at ridiculously low percent.
The Mach Tornado can be blocked by anyone with disjointed hitboxes or projectiles. Also, any character with the correct timing can line up an attack right on his head (from above). Though thats much harder >.>
To sympathize, my friends don't like it when I play MK either. I use my secondary on them, Ike. I guess winning with him "feels better" but thats probably just because I love Ike Spiking with a passion. This switch is made because a) i have a secondary i can use, and b) these are the only people I play with and if they don't agree to play with me, I get nobody except online + lag.
I will not, however, ever switch my main. Someone mentioned liking MK ever since his first appearance, and I agree with the sentiment. Even though I'm a guy and I don't find his voice sexy... heh. back to relevant things, I picked him because he fit my play style. Fast attacks but without the fast midair movement (i.e. fox and falco, the fast fallers, wario and jiggs, the side to side acceleration masters). Same reason I didn't use fox in melee, i just couldn't play with that kind of midair acceleration tacked on. Hence, sheik. But she got power nerfed.
So, I see where you're coming from, but having a main is something you should pick and be proud of, no matter what. Melee sheik and MK get the same flak. No "real" combos, no "real" skill necessary, etc etc. But a win is a win, no matter what.
Anyways, thats what I think about the subject. Just thought I'd try to pitch in as logically as possible.
Kenpachi