I read his book on the Anthropic Principle when it first came out and it really disturbed me. It just didn't seem right, it was clearly very fuzzy philosophy and I had trouble accepting much of it, but I was so intimidated by Tipler's reputation and his acknowledged contributions that I doubted my own instincts. It wasn't until I had a chance to think about it, and read some critical reviews of it from people I respected, that I felt comfortable about fully disagreeing with it. I am usually ready to concede to the expertise of others, and it is usually wise to respect authority, but there is no reason why smart people can't be very wrong about some things, sometimes even in their own field.

Now this is not the same as Fred Hoyle's betting on the wrong horse in the Steady-State vs Big Bang cosmology debate. Both sides had good arguments, and a crucial observation was missing that eventually settled the issue once it became available. It's sad, Hoyle was one of the great astronomers of the first half of the twentieth century: he single handledly did the pioneering work in stellar structure and evolution as well as nucleogenesis, some of the most critical work in astronomy ever, but today he is mostly remembered for being wrong about the Bang, and some of his weird ideas about panspermia. So it goes.