I think there are scenarios where these types of blocks make sense. Like was mentioned earlier, if you have a very small player going against someone twice his size, he can either shoot low or get knocked on his back play after play. I don't think a big aggressive kid should be doing a cut block at this age, but a smaller guy who is just trying to make it competitive should do anything that is allowed in the rules to not get blown up every play. I have no problem with this and in fact would say that this is safer for the kids than a kid who is twice the size of another just driving him on his back every play. With a smaller/less aggressive kid, I don't think there is much chance of him causing injury if he is going low on a person directly in front of him. The problems you get is when someone does a block like that on a defender who is not head up, but that doesn't happen at this age and would be an illegal chop block 90% of the time anyway.
I like the 8 man format at this age, but this is one of the problems. Smaller kids who can't be running backs because of athletic ability are forced to play on the line versus out at receiver. They better do what ever they can legally do to keep from getting hurt. Again, I think for some players this keeps them more safe. Would you rather a 50# player get knocked onto the back of his head by a 100# player over and over?? I wouldn't.
Again, I don't think its necessary for a big or aggressive kid to do a cut block. And, its not necessary for a small guy to do it against another small guy. I'm just saying situations where its a big mismatch.