It's unclear to me what is the risk to ISS. Secondary payload was on the much lower orbit, and even if it was on the same orbital plane, they could just slightly change orbit plane, and try to raise the obit with any chance of success entirely safe for ISS.
It's probably mostly a theoretical risk. On the other hand, I recall a flight to Mir that ended up slamming into the station. And NASA doesn't have any reason to accept a risk that doesn't benefit its operations.
There were no flights to Mir that "slammed into the station". The collision on Mir was due to an accident during testing of a new manual docking system for the Progress spacecraft. However, prior to the test the Progress had already successfully docked with the station, the test involved undocking and then switching to a new docking system for the test.
> And NASA doesn't have any reason to accept a risk that doesn't benefit its operations.
Goodwill in the space community and helping to defray costs of future launches by making commercial launches more successful (and thus less expensive, if only for insurance purposes) seem like things that benefit their operations. Perhaps this is a naive opinion, though.
In risk terms, the satellite that was ditched is worth absolutely nothing compared to the ISS. The ISS is the single most important thing humans have in space at the moment.
Purely on the basis that the new trajectory can't be gone over with a pin, even if all the maths comes out saying that everything is lovely, you do not refire an ISS delivery rocket that is not where you expected it to be, especially one that has already sustained damage, just to test a new robot.
