Something I don’t understand is why does everyone insist on blaming Cyborg for Martian Manhunter's removal as a founding member of the Justice League. While I understand the logic I don’t agree with it.
From what I gather the animosity is coming from the fact that they believe that DC wanted to promote racial diversity so they removed MM and added Cyborg in his place; so now everyone uses this to direct intense resentment towards Cyborg. I'm sure some of it is genuine and others have different motives for showing such animosity towards his character. For those whose animosity is genuinely directed at Cyborg because they believe that he replaced MM, the argument doesn't make sense because it suggests that there is a set number of positions in the Justice League or more specifically there can only be only be 7 founding members of the Justice League. The simple truth is there is nothing to suggest that there can only be 7 founding members of the Justice League. Perhaps if the justice League called themselves the "Super Seven", then someone would be able to make that argument.
DC could have easily kept Martian Manhunter on the team and then added Cyborg to make 8 founding members of the Justice League. The REAL reason Martian Manhunter was removed form the team is simple; Martian Manhunter wasn't on the Superfriends "cartoon". So yes they did add Cyborg for racial diversity, but they didn't take out Martian Manhunter because of Cyborg. That's like saying they removed Jean Grey from X-Men comics to make room for White Queen.
Martian Manhunter's removal has nothing to do with Cyborg so there is no reason to direct such hate towards his character. Cyborg's removal and Martian Manhunter's insertion simply coincide with one another because DC is trying to create a new founding theme revolving around the Superfriends cartoon. This theme can be seen embodied in comments made in the New 52 Justice League issues #06 pg. 20-21 and again in New 52 Justice League #07 pg. 13.
New 52 Justice League issues #06 pg. 20-21
New 52 Justice League #07 pg. 13.
This influence can also be seen in the fact the White Martian invasion origin was replaced with a Darkseid invasion which to me was a shout out to Superfriends cartoon The Super Powers Team: Galactic Guardians.
I think it's important to point out that Cyborg appeared in the last series The Super Powers Team: Galactic Guardians. By that show the Superfriends were renamed The Superpowers Team, but The Super Powers Team shared the same continuity with the SuperFriends show, that's why he's technically a Super Friend.
While Martian Manhunter did exist in the Superfriends continuity, he only made his appearance in the Superfriends comic book, but he was never a part of the Superfriends cartoon. Apparently he left Earth to go to Mars in order to help his people search for a new world.
Basically, I do understand why people are mad. Martian Manhunter has been a charter member of the Justice League since the 1970's; but at the same time I think we shouldn't suggest that means there is no room for diversity on the team.
Would it make everyone happy if in the next reboot they tried write a comic that includes 8 founding members of the Justice League:
Superman Batman, Wonder Woman, Green Lantern, Flash, Aquaman, Martian Manhunter, and Cyborg
Then perhaps they could adhere to the concept used in the Superfriends continuity, where MM leaves soon after (technically before) the creation of the Justice League to go back to Mars?