Why bother with anything then? Screw those suckers helping old people and children cross the street too.

Selling food that is past it's expiration date is a public health hazard and a shady business practice.
Gentle tried to be comic-book-heroic when he was younger and caused more harm than good so in order as to not interfere with those situations he decided to tackle small stuff that's often in the blind spot.
And his plan to hurt the business was to expose them. Since he's not a big newspaper but a youtuber with a small view count it didn't really work as planned but what else was he to do? Burn down the store?