Sad Puppies

Scorpious's picture

I was checking GRR Martin's blog and saw a number of posts referencing the "Sad Puppies" controversy at the HUGO awards. I had no idea what he was talking about, and after looking it up a bit, I still don't really ... but it seems to have to do with conservatism in sci-fi, which luckily fits into this site's remit. 

So what is it?