My advice: Don't call it a currency. Don't call it money. Don't associate it with finances. Call it social-based transactions and say it's protected under free speech; The First Amendment if you're American. That's all you have.
What we call it won't matter. Obviously, we're all here not out of some social purpose but because bitcoin is a currency. Miners like using bitcoin to make money. Others like it as a mid-or-long-term investment. Day traders and bot-makers like it because trading here is less complicated and doesn't require $25K while under a strict ruleset that fucks the small guy. Lastly, some like it only to buy stuff or to be hip.
Most people are actually a mix of the above, but very few are using bitcoin for a purpose other than as a currency.
You do have a good point buried in there, however. Namecoin, as a vehicle for speech, might actually be more protected in the US and other free-speech nations than Bitcoin.
If we can sell the idea that bitcoin is money, but money is speech (Hello, occupy wall street), then you've got some protection. Attach Bitcoin to a messaging system and you've got a constitutional conundrum. It would be interesting if bitcoin could piggyback p2p messaging on every transaction. It would be slower than email, but obviously with some advantages.
Bam! Now bitcoin is both a currency and a form of speech. Include the ability to send messages to multiple addresses, and now it's a form of the press (e.g., if I can publish a newsletter by essentially sending small transactions to every subscriber, it's press).
Hell, let's try to hit as many constitutional protections as possible:
1.1 Religion. Quick, someone found a church that uses bitcoin and this new messaging system as the sole means which the church congregates (desseminates religious communication). The principle of semi-anonymous community, wherein one believer is not elevated above others (such as to a priesthood), is actually within the domain of Jesus' teachings.
1.2 Assembly. At this point, twitter itself is probably bulletproof for this reason alone. The equivalency of virtual assembly would be a supreme court decision, but it's one more for the fire. The more that bitcoin could be used for any form of virtual assembly, the better.
1.3 Press (already covered the right to publish).
2. Guns. Uh. Crap. Well, there is a small debate that does exist as to whether newer, stranger forms of arms are covered. For example: hacker tools.
3. Homeowners forcibly housing soldiers. Shit. I don't know.
4. Search and seizure. People pay a lot of attention to the search part of this, but it's also part of the argument against eminent domain being used without judicial involvement or for a third party's advantage, which possibly applies to bitcoin.
5. 6. 7. 8. Rights of the accused, etc. I don't know how this could apply to bitcoin.
9. Other rights may exist and just because they're not in the constitution doesn't mean they can be violated, or something like that. This one is lovely for bitcoin use on the shoulders of such arguments such as freedom of privacy, free movement, biased enforcement of laws, etc.
10. Federalism. Crap. Okay I'm going to give up on this line of insanity right there.
I did those amendments off the top of my head, so they might be off a bit.