While it is hard to watch, allowing Soderblom the opportunity to get right in the NHL is the right thing to do for a couple of reasons...
There is no better alternative.
The Hawks could have claimed Antti Raanta to fill the backup goalie spot, but he was playing worse than Soderblom. Jaxson Stauber had a cup of coffee with the Chicago Blackhawks last season. He had a 5-1 record but the offense provided him a lot of goals. The offense has not been spotting Arvid a lot of leads to work with.
Stauber has a 3.41 GAA with a .890 save percentage in 13 games with Rockford this season. Maybe, Stauber could produce better, but it is not like he is a wall in goal either.
Drew Commesso is benefitting from Soderblom's struggles as it looks like Commesso is now the organization's future No. 1 goalie. He is nowhere near ready to play in the NHL. He is doing well in his first full season in Rockford, but goalies need at least a season and a half before they are truly ready for even a spot start.
This is not like the blue line where the Chicago Blackhawks have some other prospect options to work with. Wyatt Kaiser got sent down because the Hawks had Isaak Phillips waiting in the wings. This is not the case at goalie.
Thankfully, Petr Mrazek is playing well as the top netminder and has avoided the IR. Soderblom's problems have the possibility of trading him at the deadline in doubt.