That is a bit harsh an accusation.
Correct that the man is only likely to contract the disease through promiscuity. It is not beyond possibility that one of this wives or a former wife might have unknowingly had it from a former marriage. Would it have to be ultimately traceable to some haram act? I am not sure. But, it is definitely a lot less likely if everything has been halal.

Still, a promiscuous man with more wives would infect more women then a promiscuous man with one. So, even if promiscuity was the original problem, polygamy would be a force multiplier.

I don't think it is necessarily anti-Islamic to think that polygamy is a less than ideal arrangement in today's world.