1. It most certainly was malicious, if not in outcome, in intent. xach wanted to say "Look, you say you're a coder - look at me I'll show you." There were a multitude of ways he could have presented his case in a manner that would have been - frankly - much more mature.

2. This is pg's personal pet hobby. I don't think holding him responsible for every possible vulnerability is really all that practical, especially when the code is wide open. He's putting it out there with an element of trust that a hacker to be would actually provide a fix instead of being malicious. If xach was such a great positive influence, why didn't he provide a patch?