The title of the article, "when Yemen does it...", "it" is referring to blockades, misleading readers to believe that the US is labeling the houthis as terrorists because of the blockade, while the terrorist label has been applied because the houthis keep shooting missiles at ships without provocation.

The article is ignoring the weeks of being fired upon first that the US shot down missiles without any retaliatory action.

Then the US labeled the group firing missiles on ships and attacking ships without provocation terrorists.

The author seems concerned that if the people firing missiles at international ships without provocation are labeled terrorists, they might receive less aid, even though aid exemptions have been added?

Potentially receiving less aid seems like a reasonable consequence given that the ships providing aid are being fired upon without provocation by the government receiving aid.