Neighbor tree clearing

We finally decided to buy the land which we have leased for 3 years and currently have a contract on it.
There are 4 subdivided lots, one of which recently sold adjacent to ours. We have a stone wall as a boundary line and these people have a clear open field but decided to take out some very large, healthy from what I know pine trees that were very close to the wall. I saw one marked that looked like it was directly on the wall and they just took that one too. We now have way less privacy in our backyard, and the so called view they are trying to create is going to be of our new house. I talked to them about which trees they planned on taking a few months earlier but said they would just be taking a few smaller decaying ones. Come to find out, since the surveyor happened to be showing us our property lines when the logger was there, it got back to the current seller of our property. We then got a letter stating that he basically gave permission to cut down a white pine that is basically on the boundary line of their lot and the lot we are contracted to buy. He said it was before there was a contract on the land so he felt it was within his rights to do so. He also stated "he didnt want us to think they were doing this on their own." Needless to say we are furious at the him as well as the new owners who knew we have lived here and planned on buying the whole time to not even confront us about it. However I am afraid that if we rock the boat now he will pull out of the deal so my question is this, should I wait to sue them until after the sale?