I think the issue is that it is just a shitty comparison in general. The holocaust as you said was mass genocide based on ethnicity. Meat consumption is very different, exotically because we breed more each year to continue it. It would be better if they just gave the number of land animal killed for meat each year and compared that to those killed as a result of the holocaust. Saying 56 billion land animals are killed each year, the holocaust only saw the death of around 21 million, is a lot less extreme than saying THE HOLOCAUST IS JUST LIKE THE MEAT INDUSTRY. I don't think either statement is in good taste, but at least the prior isn't so hostile.