We can take a debate about Blue Cheese as to whether or not mold is a kosher thing to eat or not, (lots of people are divided on that point). But when someone states unequivocally that there is no blue cheese made with vegetable or cow rennet, that is just simply not true.
Here is just a 2 second sample search.....
Shropshire Blue is a blue cheese made from pasteurised cows' milk and uses vegetable rennet. http://en.wikipedia.org/wiki/Shropshire_Blue_cheese
We rest our case.