"The compilers, for the most part, are smarter than people at optimizing code."
No, they emphatically are not. No computer algorithm is any smarter than the people that wrote it (in fact it's always going to be dumber.) If the compiler is better than YOU are at optimizing code, that may well be true and understandable - presumably optimising assembler is not your specialty, after all.
But a competent assembler specialist (someone in the same league, skillwise, with the guys that write the compiler) will beat the hell out of any compiler ever made. There just is no question. He knows every technique the compiler knows, but he is better equipped to know when and where to use them.
Compilers serve many valid purposes. They allow less skilled programmers to still produce a usable product. They allow more skilled programmers to produce a usable product more quickly. They facilitate portability. Plenty of good reasons for them to exist and be used. But beating a competent human at optimisation tasks is not one of them.
"Java has the added advantage that it uses Just-In-Time compiling, so there's a lot of cases where Java, or .Net or any other language that uses an intermediate byte-code and actually outperform C."
I know a lot of people think this, but it's nonsense, as a moments reflection should make clear.
I have no doubt that a poor coder might find JIT improves the performance of his code, but that really doesnt justify the assertion. You would need to show that JIT can actually beat a well written C program, and it wont. It cannot. Absolute worst case, if he has to, the C coder could simply implement a VM and JIT in his program and achieve the same results - and that is a tie. C cannot possibly lose that comparison, the worst it could possibly do is tie.