Tampering is such a gray area (see Miami Heat circa 2010), but this one seems pretty blatant, at least on the part of the Hawks.
Here's an interesting take on the fine levied on the Rockets. I won't quote it all here, but you can follow the link. This is just one side of the issue, but it sounds like the fine may have been unfair to them.
NBA leaves Rockets wondering where the line is for tampering, By Patrick Harrel on Jun 10 2013, 8:04p