I Dare You

Dares are just a way for one to tempt another at doing something to prove nothing. Basically, yes, there isn't a better way to state what Mr. McCool had said in class today: it just proves you're easily manipulated. People who are easily agitated and give in to taunts and challenges are often easy to manipulate. You can basically say that you're incompetent if you can't do so and so, and they'll do it just to prove to YOU, the darer, that they can. This proves nothing, because basically it's just "okay, good job, you can do it. want a cookie?" and you had just achieved something while they had not.
Dares are good if you're the giver of dares, the darer, while they're not good if you're the one that's out there doing them. I was dared in outdoor school once in middle school to lick the wall of my cabin. I did it, because I wanted to prove to my new peers that I could do it. After I had done it, I realized: I had proved nothing. Other than my repulsive willingness to lick an old cement wall, I had accomplished nothing. After that, I analyzed anything and everything one step higher to see what can I really accomplish? Is it worth it? And then, I do not give into dares easily.
If doing a dare allowed me to embarrass someone, then yes, I would do it.
But of course, everything is situational.