Classic straw man argument. Viruses are illegal in almost every case and thus clearly they should not, and will not, invest in viruses. Not that I support IM, but they are solving a clear and distinct problem: software is hard to monetize.
I'm not sure why you characterise this as a straw man argument. GP post suggests that investing in viruses is unethical on a similar scale to investing in deceptive crapware installers.
You drew a separate distinction between those scenarios (whether or not there is a legal difference between deceptively installing crapware and promulgating viruses). I would suggest that you are re-stating and seriously misrepresenting GP's argument, rather than pointing out any genuine fault with that argument.
On a related note, in my view tying your ethical standards to whether or not a given activity is currently illegal is both lazy and far from optimal.
The virus statement was a rethorical question..
Unfortunately it is not a real problem that users face. It's a problem that a very small minority has and that inconveniences the majority. If that's what you set out to do in life..