Problem is you're both just assuming that Rosberg could take Hamilton out of the race, and get away from the incident with little to no damage whatsoever. Nico barely touched Lewis in Spa, yet it still severely damaged his front wing. As a result he lost downforce, couldn't pull away from the field before the stops, and lost the race as a result.
Now imagine what a deliberate, much heavier contact could do not just to Hamilton's car, but Rosberg's too. You only need to look back through history (Japan 1990, Australia 1994, Europe 1997) to see that the instigator of a supposed 'deliberate' contact, has never come off better than the victim. They've only ever come off just as bad, or worse.
And that won't work for Rosberg this weekend. So why'd he do it? Formula One cars are fragile machines after all, and the drivers know this. They're not tanks.