To be honest with you, I can't tell from the tape if there was any grabbing of the "jewels" or not. And, I've seen it a couple of times myself.
I'm also not sure as to the natural reaction. The last time anybody made good contact, I was about 13 years old. My reaction then was to double over in pain. :^) By the time I reached my 20's, my reactions had turned more towards the offense.
I know that there had to be a couple of witnesses that had a different angle on the situation, but I'm not sure what they saw nor am I sure what they'll say they saw. Cops tend to testify in favor of other cops unless there's some real nasty stuff going on. Similarly, neighbors in some areas are very tight and will not testify against their own neighbors and aquaintances.
I agree with one thing; this doesn't look good for the cop. But he gets a trial (though without the camera, there might not be such a trial), hopefully a fair one just like the rest of us.
I did find it interesting that the "camera man" had some outstanding warrants. The plot thickens here.
Well, remember. The allegation was grabbing WHILE HANDCUFFED which would probably not result in good contact, as you put it. Once in softball, I got nailed by the catcher making a sweep tag in an upward motion (while on the ground) when I crossed the plate. They had to wait a minute or so for me to get up from the left side batters box! But I can't think of any possible reaction to being grabbed there (or really anywhere else) other than moving away and using your hands to get free.