The problem is that you can either have FTL or causality, but not both. Also, relativity has been extremely accurate as a description of the universe, particula

The problem is that you can either have FTL or causality, but not both. Also, relativity has been extremely accurate as a description of the universe, particularly on the macro level that you and I happen to inhabit. I'd say that I'd never bet on FTL being real, but to be honest I'd be surprised if you ever found anyone to even lay you odds. And as you say, that does make SETI rather pointless even without considering that the SNR to Mars on a good day is, what, ~11 dB? We get generation ships, and if we are extremely lucky, we may have some very patient pen-pals, but warp drives, ansibles, and their attendant paradoxes are pretty unlikely to be features of this universe. Personally I prefer a knowable universe to a tourable one.