If that's what works for you then go for it. The only problem I've ever had was sorted out easily through email but I've only done it once.

I don't really view it as the company wronging you. It's a dangerous fuck up, but it is ultimately a mistake. I don't think there's any need to be aggressive, passive or otherwise. Broadcasting a passive aggressive response is a similar action to telling the store manager you're pissed. Nobody you're going to be in contact with was the line worker/maintenance staff responsible for your fucked up ketchup. Just keep it cool, let them know the serial number/production code so they can try and address the issue and ask for some form of compensation. No need to get all emotional.