I see this is related to the "free speech" thread you've started, so trying not to overstep the bounds of this question, here's my take:
By definition, no topic is categorically taboo, otherwise it would not exist. However, there is some sense in which one should consider how objectionable a particular topic is- a topic is raised for people to respond to and this is how the consequences arise. One should merely be prepared for the consequences that might happen in the course of opening one's mouth, like triggering the knee-jerks of sensitive people.
One problem is that when certain topics are generally thought to be taboo (e.g. the various paraphilias), it's not like it's going to get any "better". Usually it's like trying to hide a "problem" under the carpet which then becomes a self-fulfilling prophecy: people respond to the terms by subscribing to them and reinforcing distinctions which didn't exist prior to the rhetoric. If this has happened, then I see no point in calling a topic taboo; it ought to be discussed openly, as the ability to do such would be the sign of a maturing society.