If you and I want to hand out leaflets about the 2d Am. and we have 2000 printed up at Kinkos, and we can't have them without paying a sales tax, has our freedom of speech been abridged?
Because you are not paying the sales tax on your speech, you are paying it on the buying of the leaflets. No matter what the leaflets said, you pay the same tax. Not a free speech issue.
Now, if you were taxed specifically because of the content of the leaflets, that would be a free speech issue. Pay sales tax on the purchase of leaflets for a bake sale, fine. Pay the same sales tax for gun rights leaflets, fine. Pay any tax only because
they are gun rights leaflets, that would be infringment of your free speech rights.
Note also, your printer could charge you a special fee for printing gun rights material, since he's not the govt, he's not infringing your rights by doing that. You are free to go elsewhere with your business. It wouldn't be smart business for him to do that, but he's not violating your rights, if he does. He's just being a stupid jerk.....there might be some business laws he could be violating I don't know about that, but it wouldn't be a First Amendment issue.