Creating quality games requires a large amount of cash reserves to pay for a creative team, including programmers; independents usually do not have that luxury.
If Microsoft got to buy Blizzard it might actually cement Blizzard's future, securing the old titles and ensuring future ones. But, it might also get shut down because of lack of focus. I'd much rather have Blizzard remain independent to some degree, because then they may remain undisturbed.
Having said that, however, the arguments presented by regulators are pretty much ridiculous. They seem to only care about competition, and not about what is best for the future of Blizzard and gaming. Too much competition can ultimately degrade and obstruct the end users – I'd also hate to see that.