Free trade means not using the police power of the state to force consumers to buy goods &ervices only from approved sources. If you wish to boycott the exports of a dictatorship, do so, and encourage others to follow your lead. For that matter, you can boycott any nation or seller for any reason.
In general, it is best to expand trade and all links with the "developing" nations. Their inclusion in a network of commerce tends to militate against exploitation of their work forces.
Free trade is not just a goal, it's a process that opens societies up, brings change, enhances the flow of infomation and challenges the enemies of Liberty. No, it's not perfect, but it's better than discriminating against your own citizens -- using them as pawns in your ideological war against your perceived villains. In some cases, regime change should be imposed because the villain really needs to be removed and his people freed, but we do that with bullets and bombs, not boycotts. See The Pentagon's New Map, by Barnett, ISBN 0-399-15175-3, for more on this.
In short: withhold your money from specified vendors if you wish, but don't deny me the option to buy what I consider best for my purposes.