I'm not sure what you mean by "don't currently exist" -- there is a general consensus that some form of patent reform bill is going to pass in the not too distant future:
https://www.eff.org/issues/current-legislative-proposals-pat...
By launching the mother of all trolls to the disgust of the industry at large, they're adding fuel to the fire and making it more likely that stronger anti-troll legislation will pass. Certainly you can expect Google to dump several million dollars more into lobbying for it now. But if that legislation passes and decimates the weaponization capacity of the patent arsenal they just paid billions of dollars for, they've just wasted billions of dollars.
Similarly, the general consensus here seems to be that what they're doing is totally unacceptable. Here where we have the people who choose which platforms to develop for, whose choices collectively make or break those platforms. Yesterday if you had a choice between hiring an extra developer to develop a Windows Phone version of your app or using the money to improve or advertise the Android version, you were more likely than you are today to do the thing that benefits Microsoft. Similarly, if you're Samsung or Asustek or Huawei and Microsoft has just loosed the troll upon you, well, good luck trying to negotiate favorable terms for any of them to ship Microsoft technology in any of their products.
And on top of all of that, how can they not expect Google to respond? If you start a war you can expect the other side to return fire. Maybe not in kind (by setting loose their own patent trolling entity), or maybe they will, but one way or another it's not like Google is incapable of striking back. What happens when they throw a billion dollars into WINE and Samba? Or add support for Kerberos, LDAP and Group Policy to the Google API so that companies don't need Windows domain controllers anymore? Doing things like that probably wouldn't move the needle on Google's bottom line, but it would stab Microsoft in the face. Which is what happens when you make enemies.