There has to be some restraint, or else people will be afraid to participate in the political process.
A drug case would probably get to the point of needing a warrant much sooner, since a pro-legalization activist isn't usually directly initiating contact with the government, so the government has no business asking for information without a warrant. But if a pro-legalization activist makes public statements about their illegal activities or intentions, it's okay for the DEA to keep an eye on those public statements and to use them to try to get a warrant.
I wouldn't be concerned that a group whose politicians have on several occasions advocated: armed marches, intimidation of the other party around polls, refusing to pay tax, shoot census takers, or preparation for civil war - was "afraid to participate in the political process." I would rather be concerned that it was causing others to be afraid to participate in the political process. This IRS gaffe is covering a history of anti-democratic conduct from the very group beating its breast (even as its groups enjoy the nonprofit status which the IRS gave them long ago).