We see many times that Darth Vader does not tolerate insubordination or disrespect through his chokes.
Sometimes he follows through, other times he is told to back off,
Why doesn't Kylo Ren do the same to General Hux when he disrespects/belittles him in front of Snoke?
There are multiple times in the film where Snoke takes a report directly from Hux, or gives Hux direct orders-- this implies that Snoke finds Hux to be useful. In that situation, Kylo Ren would probably not want to harm Hux, for fear of angering Snoke.
Another issue to consider is that, in the original trilogy, Vader had fallen almost fully to the dark side. Conversely, Kylo Ren hasn't fallen fully because he still "feels the pull to the light"; he has to actively will himself to remain in the dark.
The end result is that, when Vader is angry, he casually kills high-ranking members of the Imperial military. When Ren is angry, he smashes inanimate objects.
This is answered in The Force Awakens Visual Dictionary:
He is outside the command structure. He doesn't stand above Hux (nor vice versa), he's outside the chain of command.
Kylo Ren exists outside the formal command structure of the First Order, and has a direct link to the shadowy Supreme Leader who is ultimately in charge of these forces of darkness. It is with palpable tension that the upper command of the First Order contends with Kylo, as his agenda always trumps military objectives. In this way, Kylo's placement within the hierarchy resembles that of Darth Vader in the old Galactic Empire. This is entirely by design. (Page 25)
They are equal in position:
Phasma serves as the third partner in the unofficial command triumvirate of the Starkiller operation, alongside Kylo and Hux
As alluded to in the first quote (and is quite obvious form the film), Hux is an equivalent to Moff Tarkin in Episode VI. And as we recall, Vader didn't directly confront Tarkin either, the way he did lower level officers.
