The Iran backed Shia tribes of northern Yemen live next to the southwestern border of Saudi Arabia and have turned portions of that border into a war zone since 2014. The rebels do this by continuing to fire mortar shells and rockets at Saudi towns and villages. The Saudis retaliate with artillery or air strikes and this has become part of an endless cycle of retaliatory attacks. There have not been many Saudi civilian casualties but the Saudis want to minimize the risk of there being more of them. Meanwhile the Saudis have found that shooting back promptly and profusely has not stopped the attacks but does prevent the rebels from moving across the border. [emphasis added]
Perhaps it just seems odd to left-leaning critics to see a government willing to protect its people.
It isn't disproportional as long as the enemy isn't too hurt to keep trying to kill you.
To be clear, proportionality in warfare refers to the notion that you don't use grossly more force than you need to achieve a military objective. As in, you don't nuke an apartment building that may have civilians in it because a sniper there is holding up your advance. Your own sniper or perhaps several high explosive rounds aimed at the location should do nicely.