Well here's the thing. The world health organization and others NOT influenced by large pet food companies have said that BHA is a carcinogen.
What more is there to discuss..... It doesn't matter that they use "trace amounts." Why use any at all, there are much safer alternatives. The response from Dr. Jessica Vogelsang is another problem. No one believes eating a single milk-bone in 2005 caused cancer in 2016. It's the accumulation of these ingredients and treats which increase the chance of cancer.
The FDA is a reactive group, they always come out and say, "Opps sorry, that one ingredient we said was great, well sorry it's actually terrible and may have caused cancer in thousands of dogs." Doesn't mean we ignore the FDA, but we shouldn't take everything they say to be 100% accurate. There are other groups which look into this stuff... we cannot ignore them.