Remember when I said that I understood that it was a business move? What I'm saying here is that DC is doing this specifically to force Marvel's movie out of a spot it already claimed. Dirty play, but that's what they've decided to do.
Was ASM already in the May 1st spot when Avengers was announced on that date? If so, that was a jerk move on Marvel's part.
No, but that was before Marvel was announcing releases 4 years in advance like they are now, which we know amount to nothing as these projects have neither a completed script nor director attached.
We know Raimi's Spidey 4 was targeting May 2011. Thor seemed to be the oddball out, until Spidey 4 collapsed an Marvel was in the right place at the right time. So it's pretty safe to assume Sony was going for May 2012 for the reboot, but Avengers was not going to let that happen.
The point is, Sony established the precedent, not Marvel. Tentpoles back in the 90's and early 2000's always had the event films between Memorial Day and ID. You had JP (1993) in June, ID (1996) on... Independence Day. Lost World and MIB on those dates respectively in 1997. Godzilla (1998). Those were the coveted release dates, and always have been.
With the competition so fierce these days, Hollywood had to extend that by a couple weeks on both sides. Sony was the first to try this to get a leg up on Star Wars. It was a bold move on their part, and it paid off for them. If anyone should be entitled to a release date, it's them. But they handed it off for the good of the Marvel brand (Notably because you can't release a Spidey movie every year, so that's a bit of an overstatement).
Marvel should be thankful they've had that slot for the greater part of a decade. But due to their oversaturation (Fox/Sony are in this as well), it was unsustainable, and they had to shove their **** in July. WB, which releases one DC film every couple of years, can't have a date to themselves.
So no, WB aren't being ****s. They are returning the favor (Michael Jai White, Spawn style I may add

).