They would get sued if they can't present justification for a merger disqualification. It's their job to prove there's an actual justifiable problem, it's not on the purchasers to prove there is not.
They can't just block acquisitions because a purchaser isn't nice to them lol...
I'm not sure you understand how politics works. The deal is already under heavy scrutiny in the UK and now under heavy scrutiny in the EU for the same exact reasons. Not providing the requested information is not in their best interest. I get that they have lawyers, but the American corporate culture seems to have a lot of problems adjusting to the European / EU reality when doing business.
I can actually see the EU approving this deal with heavy concessions, and if MS doesn't accept or goes to court, the deal will fall through. Court proceedings in these types of deals take years.