So is bigotry racist when it's directed at Catholics or Protestants?   How about when it's gay people? Or Democrats or Republicans? Or longhairs? I'm not questioning that what is involved is essentially the same way of thinking - but drift the term too far and it blurs things.

Except perhaps in some pretty limited contexts the term should perhaps always be kept in inverted commas. Otherwise it seems to indicate a degree of acceptance of the notion that it's all actually about something that can properly be described as "a race", which is very rarely the case.