He is a build thief. Noticed how I said thief there, and not 'stealer'? Yeah.
Anyway, it's a bit like this scenario:
Let's say you spend years building a very nice car. You worked very hard on it. All of the sudden, you come home and the car's missing from your driveway. You then see your car pulling up behind you. A stranger steps out and says "Oh, so this car's yours? I borrowed it to pick up my kids from school."
Of coarse, you'd probably be furious with some random douche taking your baby out for a drive with his disgusting kids, right?
That's how I see this.