Sorry to disagree, but having any real fighting experience you wouldn't make such a statement.
I've worked as a bouncer for almost a decade. I have scars on my forearms and back from knives.
If you wish to discuss something with me, avoid ad hominem fallacies and stick to logical discourse.
People in a guard clamp up.
What does this mean?
I have never "clamped up" when I've pulled guard. Guard is not a static position, but rather a fluid one, from which I can sweep you so I can mount you, or push you away so I can scramble to my feet.
Not to mention you clamping them up while defending against raining punches, making their choice easier.
You're going to bite me and punch me at the same time? This means your head is going to be against my body while my legs are controlling your hips. Your punches aren't going to have much power in that case.
Not to mention getting picked up and slammed down on concrete.
It's a possibility, but highly difficult.
Besides, if it's a real fight, forget about the guard and fighting from there, that means you're looking for a submission hold.
Wrong, you've been attacking a strawman, another fallacy.
I never said I would pull guard as a first manuever on the street.
If I have pulled guard on the street, it's because for some unfortunate reason, I have been taken down, by a tackle, a grab, or a throw. It is very natural for an opponent to begin pounding someone he has just knocked down. Pulling guard allows me to control that and prevent getting pounded on.
Strawman #2, you assumed that I would be searching for a submission. There are many other choices other than submission.
First off, a submission is merely a joint break that I don't perfrom all the way. If I manage to get you in a submission in a self defense situation, I can just break your arm, and against someone with very little grappling experience, it is very easy to very quickly get them in a submission.
If I am on my back on the street, my first goal is going to be to get to my feet. If I have pulled guard, it becomes very simple to sweep and roll my opponent, putting him on his back, and then allowing me to stand. Or, not mounted on top of you, I'm the one who will be raining punches down on your face.
If we're talking biting, pulling guard allows me to control your hips. From there, I can use an armdrag to pull you into a head lock which will completely expose your carotid to me. From there, I can bite you in a very lethal manner.