Most constitutions (the one in the US for example) explicitly guarantees every citizens right to free speech. Most countries also have laws that makes saying and publishing certain things illegal. In most countries with "free speech," you are allowed to put "almost any poster you want on your front door." Similarly, Wikipedia allows you to put almost any description of yourself you want on your user page.
Quite the contrary, it is important to emphasize that there is no protection for offensiveness for anyone.
I don't know what you do for a living, but suppose you have an office at work. Do you get to put "almost any poster you want" on the front door of your office? Not at any workplace I've ever known of.
This has been gone over before.
Wikipedia is not a workplace and it is not workplace safe Wikipedia may be offensive to you
Look in the mailing list archives for answers why Wikipedia must be like the two statements above for it to operate.
I don't know what you think Wikipedia is, but I always thought Wikipedia was a project to write an encyclopedia. In that respect, the Wikipedia: and User: namespaces are definitely like a workplace— just as a workplace exists for the purpose of facilitating work, user pages exist *for the purpose of facilitating the writing of an encyclopedia*. I dunno, what do *you* think they're for?
As for "Wikipedia is not safe for work" and "Wikipedia may be offensive to you", those refer to the *encyclopedia*, and they're there because any compilation of the sum of human knowledge is bound to contain information that will offend someone. That doesn't give us license to offend *other contributors* for no good reason, when that sort of offense gets in the way of our goal: to build an encyclopedia.
We have articles on racism, and those articles contain material that's offensive simply because the fact that racism exists is a bad, offensive thing that we are fully documenting. That doesn't give me license to express racist opinions on talk pages or on my userpage-- if I do so, I'm getting in the way of building an encyclopedia by pissing off the people I'm supposed to be collaborating with.