I suspect that you really aren't. Not if you are thinking it through. Sure, your statement sounds so big and pure: "I'm for freedom of expression, freedom of speech no matter what!" It is what a Red Blooded, True American would say. But do think about it if you haven't yet:
There is of course the classical question: Do you support freedom to shout fire in a crowded theater? Really? Or, in common with the Supreme Court, I bet you are okay with there being some limitation of freedom of speech in cases where it would represent an imminent danger.
Do you support freedom for a company to lie about its products to their consumers? Freedom of a company to lie about their finances to their stock holders? Freedom of a pharmaceutical firm to lie about the safety or efficacy of its drugs? Is that what you support? Or are you now going to claim this is "commercial" speech and you only meant political speech?
How about freedom of speech by a soldier in the army to harangue other soldiers into becoming anarchists? Or Nazis? Or (see below) to go AWOL?
Or (and I agree this is trickier) freedom of speech for a band of USA citizens to praise Hitler during World War 2?
How abut freedom of speech to urge others into committing a crime? Perhaps an assault or arson on your own family by a mob surrounding your house. Are you willing to go that far with your ideals?
Wouldn't a true freedom loving person approve of free speech in the examples I gave? Yet it turns out there are serious problems with each. Serious problems proven by history. And recognized by the courts ("The Constitution is not a suicide pact."). And a recognition that one person's freedom of speech may impact another person's freedoms. Which is why even the most free society imposes some government limits on "freedom of speech." And as repeatedly pointed out by others, "freedom of speech" relates to government restrictions, not to individuals. No one is forced to rent out their hall for a Nazi rally if they don't like Nazis.
Ironically, even though I am Jewish I fully agree with you that Nazis and the KKK have a right to freedom of speech as far as government regulations go. I've donated money to the ACLU when they lost other support because they too feel that freedom of speech applies to Nazis and the KKK. I continue to believe this and support it. Yet it is crucial to also remember that the Nazis are cynically using the freedoms of this country to undermine those very freedoms. It is the price we pay, but it means that their freedom of speech makes it even more important to organize against the Nazis and their evil soul mates, to educate others, to embarrass them at every opportunity, to mock them, and to denounce them at every opportunity, and to stand up against them with counter demonstrations whenever they rally their low life supporters. Nazis can say what they want- but it doesn't mean I have to agree or listen quietly, or not make as difficult as I legally can for them to convince others with their dogma. One can recognize that a pack of wild dogs has a right to the freedom of the African veldt, but that doesn't mean that one is obligated to help them (or even allow them) to dine on a bus load of children on safari.
Finally one must remember that there are legitimate limits to freedom of speech even in terms of government laws, as per the examples I cited above and which have been found to be constitutional by USA courts. The Nazis do not have a right of freedom of speech to directly threaten others. The Nazis do not have a right of freedom of speech under circumstances that present a clear and imminent danger to the people around them. Etc. They are wild dogs. Rabid dogs. Watch them closely! And don't minimize their risk to all of us!