There has always been a strange illogic in arguments against America's missile defence program. When it was first announced as a research project by Reagan in the 1980s, the most frequent objection I heard was that it didn't work, and this was true. Had such a technology existed and worked well, there would have been no need for Reagan to commit funds for research. The program was started precisely because the technology did not at that time exist. This aspect of debate at the time could be summarised as follows:
Pro: We can't do this yet, so we should start some research.The same objection still exists, in a mutated form. Now that the technology has got to the stage of trials, it has become characterised as "unproven". The new dialogue runs as follows:
Anti: But we can't do this yet!
Pro: OK, we've got some stuff but we need to test it.Obama is a carrier of this argument. It's getting a bit strained, though.
Anti: But you haven't finished testing it!
Incidentally, in the 1980s another form of argument against the program was a bit convoluted, but suggested it would cause a new arms race and "destabilise" relations with the Soviet Union, and I guess this was right. Less clear is what might have been wrong with destabilising the Soviet empire. Today, the whole of Eastern Europe is free, and the missile defence program played a small part in winning this freedom.
That's a good thing, unless you're the sort of person who felt the fall of the Soviet Union was "the worst day of my life".