Except this doesn't apply here in the least. Microsoft has a lot more to gain from strict patent enforcement than it has to lose. This is hardly a good reason for Microsoft to give up all of the effort they've put into their software patent portfolio.

I don't think they have enforced a single patent and they have paid out ~1billion to patent trolls so I find it hard to believe patents are a net gain for them.

What about collateral damage of such enforcement?

Microsoft will do everything in its power to make sure it can sell Office. They have tens of billions of dollars to ensure that this doesn't happen.