Is participating in professional forums good or bad for my career?
I work in a much less controversial field (I mean, in an uncontroversial field), but I've been participating to various online communities for more than 10 years, first during the newsgroup era, then in forums and now mostly with SE. So, let me share a few ideas.


  Could participating in online professional forums related to my field become a hindrance in the future for both my Ph.D. and future work?


I don't have any hard data: in theory, it could; in practice, unless you do something egregious, I doubt. And many forums are actually virtually unknown to the wider audience (see e.g. this meta question of mine about Academia).


  Should I "scrub" my presence in these groups (especially the one that are more social than academic and accredited)?


I don't think that dropping your participation is warranted, but consider the following points:


Check if your university has any policy setting boundaries around the participation of employees or students to social sites (e.g. public shaming of your university can lead to expulsion).
Beware that as a professional in your field you might have a different perception of certain topics with respect to untrained people or people working in a different field. Things that can be obvious to you might be difficult to understand from another field's point of view. And this can lead to controversy. A curious (non-serious) instance is the following: I've been criticized on the only answer of mine on this site related to my profession.
Disengage early from lengthy pointless discussions when you see that they are draining your time and energy. As a young researcher, you should now be focused on building your background knowledge and producing your first valuable works.