People who just hate any and all DLC are pathetic. If they had it there way, we'd all still be rocking flattops, playing Pacman and awaiting the next Back to the Future movie, asthough we're all stuck in an 80's timeloop. Take your nostalgia goggles off and and eat 'em.
It depends on the DLC. Day one DLC is a very iffy issue.
If it adds in a decent chunk of new content - a new character or items or stages then its worth it.
if it is just costumes or decals then it is pointless.
Given that this is free, it renders a large chunk of haters arguments void.
Likely this was additional content that was almost but not quite ready when the game reached the release phase. rather than delay release, the team chose to develop it as a DLC pack that would be freely avaliable when the actual game goes live.
If your zergling rush fails, consult your hatchery. You may need more zerglings.