I have had someone do the same thing. He has my great-great grandfather from the paternal Finkelstein side of my family in his tree as well as my great-grandparents, all of their children and the documentation I had attached to all. Clearly those two generations are all deceased. He stopped there although my father's generation is also all deceased, thankfully, he did not add them nor, the succeeding generations.

I have messaged him three times requesting proof of the relationships and he has not responded though I know he has read my message. I even sent emails to some people in his tree but they have not responded. 

Not as many as some but I have spent over 10 years working on my trees and I really resent someone doing this. This also  happened with someone else's tree and when I contacted him he said it was too bad I hadn't made my tree private. He also didn't have any paper trail. Needless to say, both of these people have over 10,000 people in their trees. Somehow, for people who take their trees seriously, this is not an appropriate method of building trees.
Naomi Finkelstein
Winnipeg, Manitoba Canada