DY, North Dakota’s use tax was struck down (Quill Corp. v. North Dakota, 504 U.S. 298 (1992)) by SCOTUS. The Illinois Supreme Court struck down that state’s use tax 6-1 (PERFORMANCE MARKETING ASSOCIATION, INC.v. HAMER), Some states have tried to get around it by making it into a type of surtax on income taxes but until and unless Congress acts (the Senate passed a bill three years ago but the House has yet to pass it). Of course, one can get around NY’s completely by having the merchandise delivered to a friend or relative in NJ, which does not have such a tax.
As for criticizing other people’s failings, there is a mitzva to inform someone when he is violating the Halacha if he is generally observant. It is certainly a mitzva to make a general observation that something is prohibited.