I feel like penalizing Curry because his team is better is a bit unfair.
The Warriors are arguably the best offense in the league through the first half of the season. Best shooting percentage, most assists per game, #2 in offensive efficiency, most points per game, etc. Curry's supporting cast is damn good, but they'd fall pretty hard without him. I mean who's our second best player, Klay Thompson? I love him, but he averages 2 assists a game. Curry is what drives the offense and is why the Warriors have been so good on that end. And some of that doesn't even show up in stats. His immense gravity on offense creates gaps for others to score even when he's playing off the ball or when he gets hockey assists.
So while Houston without Harden would go from a solid offense to a bad one, the Warriors would go from arguably the best offense in the league to a middling one. Different parts of the spectrum to be sure, but similar falls in my opinion.
What they do on defense is a bit murkier and neither is great on that end. Curry does lead the league in steals as a member of the #1 defense, though steals can be misleading and he's no doubt buoyed by the great defenders around him on Golden State so maybe that doesn't mean much.
edit: to be clear, I'll have zero issue with Harden winning. And I expect the Warriors' excellence to slack a bit in the second half so Curry's MVP case could weaken as the season goes on. I just think he deserves to be up there right now with anyone else in the discussion.