At some point I figured the guy who took mine needed it more than the effort I didn't take to lock it up.
I find cars tremendously annoying and dangerous, does that mean I can start smashing them up?
Also, they are not being only vandalized, but stolen, which would imply that the perpetrators do believe the scooters are quite useful, but simply don't want to pay for them.
You're also ignoring that many of the scooters are being stolen not vandalized, or the vandalism is part of the theft (ripping off the GPS unit so the scooter can't be tracked).
Besides nuisance/boon is not a binary switch. Even if the vandals were a handful of angry cranks who were annoyed by the scooters, that doesn't imply that the scooters aren't overall beneficial to the city.
Petty crimes like this ruin otherwise helpful ideas. In my city I've come across a number of Bird scooters that have been vandalized, had the GPS ripped off to presumably steal them for personal use.
If nobody does anything about that, an otherwise great idea that could seriously help people get around more easily and reduce traffic and pollution will simply not work, because we allow some people to get away with being assholes.