Absolutely. Just to clarify, my problem isn't with Marvel or anyone else trying to increase diversity in their product, it's specifically the mass adaptation of existing characters (many of which are iconic) at the expense of existing fans of the series, some of which will almost certainly fall within these so-called minorities themselves. I'd like to think that most fans of these comics aren't thinking in terms of 'Iron Man is a womanising, rich, white, male', and more that 'Iron Man is cool, smart and attacks bad guys'.
As a few have commented, if people care deeply enough to want a character with a politically-correct background then new characters ought to be created for that purpose. Marvel have introduced a number of these as well (e.g. Ms Marvel) so I don't know why they still feel the need to modify existing characters. It's not just one or two of the traditional characters, either, it's practically all of them.
As you say, though, the more pertinent issue is people focusing too much on labelling one other instead of actually debating things properly (e.g. political issues more important than comic books and TV show castings, such as immigration and religion). People seem to bracket themselves in one group and dismiss the other side by default, it's just hugely unhelpful.
I've not seen the film, but based on the synopsis surely the point is that the Tooth Fairy is as counter-stereotype as possible? For maximum, ahem, comedic effect, he must appear unsuitable for the task at hand, much like Vin Diesel in The Pacifier. Then they can miraculously turn it around etc. etc. In either case they seem appropriately cast for the role, again albeit due to the stereotypes making that so.
The controversy seems to kick in most when political correctness alone is used as a justification/driver for change, rather than simply being in place to assure that the change can happen if needed. In such cases, it's Equality of Outcome instead of Equality of Opportunity. It's not obvious whether the BBC have made this decision because they have identified an opportunity to improve the show (in which case, great), or whether they have simply done it to appear more PC (not so great, in my opinion, and far more likely to annoy fans of the series). Obviously you'd get people complaining either way. I think most of the complaints I've seen have came from people who have perceived the decision to be made purely because of PC reasons. They're entitled to their complaint as a result.
For what it's worth I agree that it's a sad state of affairs when something like this is announced and instead of discussing the merits of the actress and potential storylines etc. the arguments become gender-based.