How to report people terrorizing the lobby
Solution 1:
I searched for this previously, and no, there is no way to report them at the moment. I do hope this feature will be implemented soon.
Solution 2:
Sadly you cannot report people who abuse in the lobby. But you can ignore them by clicking their name and choose "Ignore Player".
This is a great idea you should post your idea/suggestions at http://dev.dota2.com/. Though I think they will most likely not implement this before every other things is settled.