No, trolls who want diversity are trolls. They don't cease to be trolls just because their slap a veneer of genuine social causes on their antics.
And a huge part of the "Social Justice Warrior Narf!" debate stems from people being somehow unable to tell the difference between trollism and genuine points. So a student pointing out to his professor that some comment he made could be considered racially insensitive and might be an example of microaggression is a legitimate point. That same student organizing thirty classmates to picket the class and demand an apology from that same professor? That's just trolling on a larger scale.
It is not normally very hard to tell the difference.
The FACTS as far as this thread is that diversity in television doesn't reflect the demographics of the general population, for a variety of complex reasons both historical and practical. There is an element of discriminatory hiring involved, but it is difficult to know to what extent racial/personal preference plays a roll in hiring practices without looking at the circumstances of individual cases. It is also true that media portrayals of certain minorities -- particularly, transgendered men and women and some less represented ethnic groups -- are usually subject to the constraints of a writer's imagination, which more often than not is limited by experience. The lack of diversity in those cases can be associated with a lack of diversity in the writers/producers' personal experiences. There are relatively few cases where such minorities were actively excluded from the cast of characters or from the story as a whole; there are equally few cases where minorities were actively inserted into the case purely as a bid to be "more inclusive," as here again we see such creative choices being influenced by the experiences and/or wishes of the producers themselves.
tl;dr: The "we need more diversity" debate is an issue with a huge amount of nuance that doesn't boil down to just one cause or one specific combination of causes, nor does every situation derive from the same circumstances. Which is why I am not shy about pointing out the huge amount of bullshit trollism fouling the debate; trolls do not care about nuance or subtlety, or about dealing with reaching any actual understanding from either side. Trolls are singularly interested in getting attention, and therefore cultivate outrage at every opportunity.