Earlier quoted context omitted.
Abstracting this basically yields: "Random stranger X did something that is not right to do, so I'll hurt another random gal/guy Y for that"? Dear god, I hope you live really far away from me.
I agree with your thought process. I myself would never do that and I definitely don't endorse it. OTOH, if we apply this principle to the scooter riding population, we see that the people who ride these vehicles on sidewalks are hurting random gals/guys too. These riders made a conscious choice to defy the vehicle code -- and for what? Having some fun? Failure to plan their route to include a little more time? They…
If we apply this principle to the scooter riding population, we have no idea whether the person who's brake lines were just cut is going to be riding on the sidewalk in the first place. Heck, even in the case that the next person to use the scooter does ride on the sidewalk, cutting their brake lines greatly increases the risk to the ordinary pedestrians around them -- which was the whole thing that sparked the vandalism in the first place!
Riding scooters on the sidewalk is bad, but not comparable. One is negligence, and the other is a premeditated attempt to hurt someone who may or may not even have done anything wrong in the first place, while simultaneously greatly increasing the potential harm to everyone around them.