I don't see what the fuss is about. Why shouldn't Facebook try to provide the best user experience possible?
We live in an increasingly connected world, so this tight integration between different products is absolutely critical to a positive user experience. Would people complain if any other company added Facebook login to their product? No!
It's good that at least one company these days still cares about protecting its users from viruses and malicious software. I feel like most other companies are just not doing enough.