Whoever it was, be it a MOD or not, was unjustifiable to chew you out.
They were just probably mad or jealous of your awesome drawing skills or upset because they are fat and can't ever look like this, because they don't want to invest the energy and commitment to lose the weight and maintain it.
I am telling you with ALL SERIOUSNESS, you WILL NOT get this image or yourself suspended if you remove the MATURE content warning.
You just have to accept the fact that this is the internet and it brings the worst out in people because they can get away with it and nobody will admonish them for it.
They really are insecure cowards and some of them trolls who feed on fear and reactions. Once you stand up to them and stop reacting to them the way they want to react you'll find that they will just move on.
People get butt-hurt over the most ridiculous thing ESPECIALLY on the internet, and if they start cussing you out it's best to just ignore them and rock on. Now put on your IDGAF pants and remove the MC.