Considering what goes into the more hard-core outfits, they deserve respect for their dedication. And there are lots of outlets for that too, which is great (e.g. SCA).
However, if someone gets their tabbard in a bunch because some sci-fi cosplayers ruined their sense of immersion, at what is arguably a pay-to-enter medieval-themed shopping mall, they may deserve what they get.
A lot of the Faire folk I have met are just happy people are participating and having a good time, and if you put effort into a costume, even better.
These people are the backbone of every Faire. Huzzah!