Free thought is one in the same with free speech.
The problem is society is turning more so into a bunch of cowards now days, and if something is offensive, these like-minded cowards want this offensiveness prohibited.
You have the human right to think about whatever you so please to think about, and for anyone to object to that, your brain should be censored with a .45 colt.
Sure one has the right to freely think, that another person shouldn't be able to freely think about something else, that one may deem taboo, but one has no right in enforcing what others may not think. One only has the right in enforcing what others may think, and that is, one may think of anything and everything.
For example, the thought that someone has no right in being racist, verbally or mentally, is more asinine than the racism itself. Then again, thinking someone has no right in being racist is a free thought, so to prohibit the free thought of racism, just makes the first party who wants to prohibit such free-thought, a hypocrite.