If the user got there, or could get there, from a Google ad, reporting them might get them to change their ways.
However, consider these other possible issues: If you got to your competitor's site by clicking on their SERP results, and not a sponsored ad link, they can do whatever they want, and are not bound by G's advertising rules. If you got there by actually clicking on one of their ad links, you may be guilty of click fraud. If you typed in their Ad's main displayed URL in your browser's address bar, it may not be, and probably is not, the complete landing page URL specified in the ad.
Funny because I received an email from Google telling me my site was exactly doing that, that the back button wasn't working, but I didn't do anything of the sort, didn't put any script or anything that could do that for what I know, and I tried the page and the back button was working so... ?