In the eyes of someone who truly believes this is a politically-charged witch hunt, trump’s excuse for shutting it down might sound a lot more in the “necessary” category rather than “obstruction”.

Let’s put it this way, if they opened up a 71st inquiry into Benghazi or emails or whatever, timed right after Mueller found something big in the Russia investigation, and used the ongoing Benghazi investigation as an excuse not to pursue the Mueller findings, you might be ok with shouts for “shutting it down” because it’s “a witch hunt”. Granted, in that case it would be. I’m just trying to illustrate what might be going on in their minds.