It is also a crime to tackle a person on the street. However if you tackle someone who just robbed a bank, nobody will judge you for tackling him.

Similarly in this case, the ballots from the 2020 election were supposed to be preserved for two years. It would be a crime to shred them. This citizen has (seemingly) uncovered a crime, and an ordinary person would say that this public interest act of service vastly outweighs any concerns about whose trash is whose.