The only personal experience I have with a .32 ACP...
While skinning a huge bear this year, I started finding lumps in his fat on his legs. Cut the tissue, and inside is a nice little .32 ACP round (had a Game Warden size it with a gauge). This bear had been shot many times (we found 5-6 I think) with a .32 ACP. None of them penetrated significantly, or seemed to have done anything but piss him off.
I understand that a bear is not a good analogue for a human. But even on his legs (where the skin and fat are pretty thin) the bullets didn't appear to make contact with muscle or bone. They went into the skin, lodged in the fat and stayed right there. I think this would be somewhat comparable to a person wearing clothing, though I would expect to see some damage to organs on a person. Will it stop someone... I highly doubt it. Will it piss them off, absolutely. Will it discourage them from continuing to attack you, situation would depend.
Just my .02