I don't have a problem with your argument. However, if we don't look we will never know.
IMHO, SETI is a win-win situation. If we are alone (or other races cannot be detected), that in itself is extremely profound. If we are not, that is equally profound. So SETI in either case will give us a better understanding of our place in this universe.
I guess we are mostly in agreement then, as I have no philosophical problems with SETI. While it is unlikely to produce results in the near future, this is hardly an argument for not trying, with the caveat, of course, that private money is being spent.
But I think the author's larger point is an important one. The Drake equation is assumption presented as science, and while it is largely unimportant itself, it has become a dangerous pattern in science as a whole, especially politically charged areas like environmental science.
Take for example the relatively recent media, and *scientific*, scaremongering on both ALAR and DDT.