The corporations in this instance are essentially exploiting bugs in human biochemistry ("we like fat and sugar even when we've already had enough resources");

The corporations in this instance are essentially exploiting bugs in human biochemistry ("we like fat and sugar even when we've already had enough resources"); people are making these lifestyle choices at least in part because the corporations are actively influencing the choices. Once you grant that the corporations are at least partly complicit, it's just a matter of multiplication. If the corporations can degrade enough people's quality-of-life, then in principle yes, they can ultimately have been Worse Than Hitler (TM). So the question is actually, "To what extent have the corporations degraded people's lives?", and if you really must be binary, "Are the corporations Worse Than Hitler (TM)?". You are simply not addressing the actual question; you have answered the question, "Is murder equivalent to someone making a certain lifestyle choice?".