1) Because many of the players here (or a big percentage of) are PS3 players exclusively, so of course they'll hate on Microsoft.
Actually I think thats incorrect to say. alot of us here(myself included) are both PS3 and XBOX360 players. We dont care about the company behind the system, we care about what the system offers us.
2) People were hating on Microsoft's rumored "Xbox 720" after the PS4 was announced back in February, even though they didn't know anything about it or even it's name. I remember reading hate topics on Gamefaqs in March how people hated Microsoft, mainly due to the rumored "Non-used games" topic generating most of the fray.
And if one console is offering used game sales, but the other wants to restrict it, yet its something that we already have current gen, why wouldnt they be upset?
3) PS4 and Xbox One are both equally great systems, both worth purchasing. Don't be scared to talk back to the Xbox trolls who have no intention of getting an Xbox One. And if you're complaining about having to buy games "new" then there is a strong chance you're a person who probably wouldn't go out and buy a new console anyways. (At least not for a year or more).
I dont think XBOX ONE is worth purchasing at all, and my argument as for why is because of DRM. I know alot of other people who DO buy new games, and new consoles - myself included, who feel the exact same way as i do. It has nothing to do with the amount of money we have to spend, it has to do with the moral ratifications and restrictions imposed upon us by the services that the XBOX ONE provides.