Matthew Yglesias made the same point some months back:
Robertson is far less influential than he once was, and isn't in a position to pull strings among conservative elites in Washington, but he's good a big audience and can't just be written off as meaningless. Certainly in a world where rightwingers seem to think it's fair to attribute Michael Moore's movies to the leadership of the Democratic Party, it's worth being a bit concerned about the Rev. Robinson's views. It should also be noted that the leaders whose star has risen as Robertson's has fallen aren't exactly paragons of good sense themselves. Take a look around the website of James Dobson's slick and hyper-influential Focus on the Family and you'll see what I mean.
Matthew also links an essay by Byron York, that illuminates this. I found this interesting:
According to Nielsen Media Research, The 700 Club, aired each weekday, has averaged 863,000 viewers in the last year. While that is not enough to call it a popular program, it is still a significant audience. It is, for example, more than the average primetime audience for CNN last month — 713,000 viewers — or MSNBC, which averaged 280,000 viewers in prime time. It is also greater than the viewership of CNBC and Headline News.
The guy may not be driving policy and political discussion, but he's not just some harmless flake saying stuff that everybody by consensus agrees to be stupid.