My question isn't if you find them repugnant or not. My question was exactly what power they have to "screw up" the country. Clinton may yet run for president, so she may yet be in a position to do some damage, but today the Democrats couldn't pass anything in the Senate if they wanted to. Moore? He makes movies, not policy. Kennedy? He's a relic in the minority party.
In what way are they "screwing up" America, when they have no ability to implement their agendas?
I can see it two ways, and it depends on the politics of the author.
A liberal might say these people are "screwing up" America because they're too far to the left, causing moderates to move to the right.
A conservative would say that while they have no power, people still listen to them.
In modern America there's plenty of ways for a person to spread their message, accurate or not. We've all seen plenty of examples. A "celebrity" especially can easily find a sounding board for their opinion, regardless of how informed it is, or how many people agree with it.
I'm guessing that the author is conservative, and is trying to show what an influence these people have on the public, despite not having the power to directly shape policy themselves.
Sheep are sheep (or "sheeple") no matter what their politics, and thinking people at either end of the political spectrum will fear "sheeple" at the other end.