This is the general problem with having a bunch of laws sitting around that allow the government to punish people for things ordinary people regularly do, but then exercise the "discretion" not to punish them until they do something the government doesn't like.

Because then you don't really have any rights. They can't formally punish you for speech but they can punish you for breaking the same unrelated law a million other people broke without knowing and that only you were prosecuted for, "coincidentally" right after you said something they didn't like.