That is how this battle is going to be fought. Not regulations or laws. But by penalizing these companies abilities to label something in this manner.
A Hate Map by the SPLC is pretty generic. But look at what happened last August.
A conservative Christian media group has slapped the Southern Poverty Law Center with a defamation lawsuit after being listed alongside neo-Nazis and white supremacists on its “hate map.”
D. James Kennedy Ministries filed a lawsuit this week in federal court in Alabama alleging that the SPLC “illegally trafficked in false and misleading descriptions of the services” offered by the ministry, subjecting it to “disgrace, ridicule, odium, and contempt in the estimation of the public.”
https://www.washingtontimes.com/news/2017/aug/23/southern-poverty-law-center-hit-with-defamation-la/
Until it can be shown that anyone else besides Trump Jr saw the warning message - there is no defamation.
Considering HE is the one who reported it - and not legions of his faithful followers - that seems a real possibility.