Board Thread:Wiki discussion/@comment-27713352-20170418071143/@comment-2112031-20170418102200
The term "turncoat" specifically refers to someone who switches allegiance from one side to the opposing side.
While Abbas was certainly corrupt and broke the tenets of the Creed, he never actually abandoned the Brotherhood and he never collaborated with the Templars. Al Mualim himself barely even qualifies, as he only worked with the Templars briefly and ended up betraying both groups.
I think it's better to refine our use of the term turncoat in order to better apply it, because Jack the Ripper is currently listed as one even though he never came even remotely close to being a Templar, rather adopting a more extreme and fanatical interpretation of the Creed.
What exactly do you mean by "followed him"? If you mean that in the sense that they attacked Masyaf after Altaïr's failed mission, that doesn't really have any relevance to this discussion, except that it illustrates that breaking the Creed does not make one a turncoat, as Altaïr wasn't working together with them.