Well I know I haven't got a degree in matters religious, but even so I don't know how I'm supposed to know that Ashers is a biblical name. Although I can't be certain, I have my doubts as to whether the commissioner of the cake knew it either.

You are not a bigot for thinking something. You are a bigot if your utterances or actions cause disadvantage to a person or a particular group of people simply because of your prejudice.