1) The Department of Commerce is an executive department. That is why there is a Secretary of Commerce that is a member of the president's cabinet. It is literally called a "department" because it is a department of the executive branch. Maybe you are the one that should take a pause and realize you don't know what the fuck you're talking about about.
2) the role of the department of commerce, its congressionally authorized role, is to promote growth of the economy generally. It isn't to prop up a particularly favored entity. It is absolutely improper for the secretary of commerce, acting in official capacity, to pitch the purchase of Tesla stock to the general public. At least if we were talking about pitching the actual cars I could see an argument for it being within the scope of the "commerce" job.
3) conflict of interest rules exist to prevent someone having their private interests interfere with their public duties. Elon's relationship to Trump and his position as a quasi government official, absolutely creates a conflict of interest when another government agency tries to influence the stock price of Tesla. It is the same problem as if the Secretary of Commerce starting imploring the public to buy Trump's stock. It is blindingly obvious that this is improper. You're not winning this argument.
4) State government's and their officials are free to criticize private companies. They do it all the time. They even bring lawsuits against them. (E.g., see Texas AG's statements and suits against many private entities). There isn't anything categorically improper about it. Further, from what I saw of his comments, I don't think they were made in his capacity as governor.
5) as discussed in the other posts, there is a universe of difference between a general industry promotional event with several major industry participants and begging the public to buy a particular stock. They aren't the same at all. Stop trying to argue that they are. You just end up looking even more stupid and ignorant.