Until you can prove that he can, it is your opinion (and opinion alone,) that he can vibrate through people. Let's work on facts please.
There is a certainly a limit to what he can detonate, he can't even vibrate through very dense matter. No, Hulk's body isn't made of adamantium, but it is incredibly dense, and it is also described as "virtually indestructable." If Flash has a hard time vibrating through dense matter, what makes you think he can vibrate through Hulk? Or Juggernaut?
Hulk has never said "I can't fly," but he does something very similar; he can jump into the stratosphere, or further, and he can cover miles in a single, casual jump. That's alot like flying isn't it? Does that mean he can fly? Of course not, because he has never flown. The same logic holds true for Flash. A person is not a object, it is an organism. There is a big difference between making an object explode and making an organism explode, one of them being the apparently drastic varience of Flash's power level. If he can make objects explode, he's powerful. If he can make ANYTHING explode, he's virtually unbeatable.
Until you prove that Flash can vibrate through an organism and cause it to explode, don't use the argument.