Not to disagree for the sake of disagreeing (because I agree with most of what you said), but i think that the office of foreign assets control has been around for a while (even before the emabrgo) and wasn't invented to steamroll rights. OFAC was organized to maintain sanctions, and eventually to track activities with foreign nationals and entities as associated with terrorism, money laundering, and drug trafficking among other things. The problem is not OFAC or the PATRIOT Act, it is the embargo - and it certainly is a problem, but that's just an opinion.
I completely agree with everyone that accepting this as a possible consequence is just table stakes if you want to "trade with the enemy". If anyone is interested, you can go onto the treasury site and reference updated lists of actions taken against those who are found to be in violation of the embargo.
Edit: If I was in possesion of one of those letters, I think the only person that I would share it with is my lawyer. While they may just be fishing, I don't think that sending the letter to the editor of a well known cigar magazine for their use would be at the top of my list of intelligent things to do. Maybe I'm just paranoid...