There are no good ads, there are no bad ads. There are only threats. Malvertising is a real threat and minimizing your exposure to this threat is your best defense against it. In the InfoSec industry this is called reducing your attack surface.
These threats are very real and so are the consequences that go along with them. The costs are tangible in the form of downtime, business disruption, ransoms, and human technical resources. We have seen attacks against governments, schools, businesses, hospitals, police departments, and our homes. This is one of the newest and easiest vectors of attack. Nobody is guarding this gate until now.