The energy amount the rocket impacts with is dominated by its speed, not its mass. A small, fast-travelling projectile can make a hole in just about any kind of armour. The terminal velocity is quite low, but that's in part because of the way it is engineered — an ICBM would probably be able to put a hole through a ship deck with ease.
There is a lot of reasoning by analogy vs. reasoning from first principles going on, and the latter seems to be winning. But the main driver of the space industry is governmental funding, not commercial. Much of those statements were probably political; SpaceX have prevailed, and indeed found some champions of their own (John McCain is rabidly behind them, and some of the statements he comes up with are ludicrous in their own right, for example), though not before enduring some setbacks.