It's a legitimate military strategy to disrupt trade and supply.
I don't condone this by any means but "terrorism" is not a synonym for "violence we don't like".
This is terrorism, it's asymmetric warfare by a military that controls a territory the size of Ireland.
The west has been involved in bombing Yemen for years now.
We call it strikes against "terrorists" and "rebels" but if you live there it's just war.
It's worth noting that there are only 2 ways a war ends. A negotiated peace, or one side being wiped out. I'd rather we didn't wipe out a large part of a country. So I'd like us to skip straight to diplomatic talks.
Our first demand would likely be to de-escalate and cease violence.
The first demand from the Houthis would probably be to stop supplying Saudi Arabia with weapons to use against them. And also to cease violence.
Beyond that it gets complicated. Not a simplistic story of terrorists and bogeymen.