No, it wasn't juvenile. It needed to be said because Romney's implication that our Navy is weaker or even comparatively weaker than it was in 1916 is ludicrous.
Yes... it was juvenile. It is beneath the Office of the President to speak to anyone in such a demeaning manor, let alone a candidate for that office... granted, there is little that this President seems to think beneath his office.
Speaking of misrepresented arguments... look what you did there!
Think about this for a moment... do you really think that Mitt Romney honestly thinks that or implied that the US Navy is weaker today than it was 100 years ago? Really?
There are more than a few ships in the modern US Navy that could, on their own take out every single US Navy ship of 1919... in fact... I seem to remember a movie with a similar concept.
Do you know what a blue water Navy (like that of the US) is for? Projection of force!
What happens when you have fewer ships today (even if vastly more powerful than those of old)? The area over which you are able to project force is reduced.
Granted, the 2-MTW doctrine has been under attack for quite some time... and a smaller Navy is a way to achieve that end.
Now... if you would like a weaker military... please say so... but don't try to so clearly misrepresent what was said.