@pigsick57 when you vandalise a friend, the person may suffer a sudden drop in righteousness value. When this happened, he will no longer have a nice five star and also may suffer a very small decrease in bonus %. The person need to bring up the % by using things like training walls or the Nero wall from the Casino. I ever need to put in 30 such walls to bring up the %.
I am ok with ppl vandalising me though at the current stage. But as a beginner with little resources, I was quite annoyed. I got a couple of friends I vandalised to and fro frequently too. In fact at one point, I played by vandalising people to show that I put in the effort to explore their town and to find that item for vandalising.
But one established game friend was unhappy and unfriended me. I even got a private message from the person 'reprimanding' me because I ruined the perfect stars and also created the need for the person to redesign the perfect town to up the righteousness.
So it is up to you whether you want to vandalise. I welcome vandals and it showed that they put in effort to go through the town and it is amusing too.