Killing people would be worse than targeting them for "tax purposes" provided that those who were killed had not declared themselves enemies of the United States and gave support to organizations who intend to murder citizens of the US and engage in wanton destruction within the US. Those who do so have warranted removing the safety on the "gun" that may be used to kill them. The actual use of deadly force against them is a point of some controversy. What should have been done for the filers of the 501(c) 4s was within say 3 mths the IRS would give provisional approval but notify them that they cannot engage in advocacy of any political candidate or Party including notifying their members on what politicians support what or what members of Congress were supporting the issues that concerned their organization. Also any advocacy that they have done before approval would be subject to taxation. The IRS did not do that instead they requested info that the IRS was not entitled to such as donor lists and member lists, they requested copies of information including all Facebook posts on their Facebook account, some were further targeted by FBI and BATF as part of the investigation. This made the approval process take years.
The use of police powers against the Citizenry to suppress their Right of Assembly and to Petition the Government for a Redress of Greviences is more severe due to the numbers affected and due to ablity to limit the destrcutive effects brought by government. Indeed the killing of these four people may only be addressed by such petitions and assemblies and then can put and end to it. It is a matter of scope, if the President exceeded his authority in the killings we can address the issue in Petitions in Congress as long as we can keep that Right and not have it suborned by a President that is continuing down a path that leads to a Police State and where unapproved ideas and speech is silenced.