I really can't be bothered writing out a huge thing so I'll just "borrow" some of Sparky's because it pretty much sums everything up.
As Sparky once said (slightly modified):
Because you have all rejected everything I say and made difficult everything I desired to do here.
Because you systematically trolled all my posts, whether in General Discussion or the Halo Demo subforums.
Because you have only implied with everything you said that I should leave, even with the forced responses of "Oh Sparky we value you and what you do," and because those responses in their contexts could only mean that the only value you find in my presence here was that it allowed you to exercise abuse and bullying against me, pointedly.
Because nobody here has shown interest in even my most extensive projects.
Because I was patient with this forum and its visitors since the beginning of this forum.
Because despite my history and experience and expertise here I was still shown more respect by Halo Demo gamers than by my fellow MGM modders.
Because this forum has digressed into a troll festival.
Because I am now completely ignored by most of you.
Because I can no longer do any good here because of all previously said and more.
I, Samuco, quit MacGamingMods.com and its related communities.
All my HaloMD-related activities will cease.
You all have no more part in my life. As you have rejected me and everything I do, so I reject you.