OP: as a fellow MMMP cardholder with a stinky garden, I offer the suggestion of investing in some stovepipe, mount it to your building, and exhaust above roof level...
Or tell the guy to fuck himself. This is Michigan, we get turkey shit, chicken farms, 3 week manure spreading marathons..... we don't get to tell the farmers to shut down or we will call the cops, cuz we don't like the smell.
Keep ur grow room locked, and your amount on hand under 2.5oz, stay under the 12 plant max.... and if the cops DO come knocking, take a deep calming breath, answer politely and respectfully, with both your state ID and MMMP card ready when you open the door. Tell them they are welcome to view your garden for compliance, and even stand outside the house to see if the smell gets them addicted.... when they look at you funny, say your sketchy neighbor said he would call the cops on you for that reason....
They will look at eachother.... apologize to you. Possibly ask if the neighbor was aware you were a legal MMMP cardholder, and if such can be proven, they may even write a citation to the neighbor for misleading them to get them out there. Or at least knock and let him know its all legal.... and by the way, what are those marks on your face?
NOTE: They are only invited in IF they are there for the reason of your cannabis. They do not get to look around for anything else to try to pin on you, its not an open search or fishing expedition. If they say there is suspicion of 'marijuana' inform them that the plant is called 'cannabis' and police shouldn't use slang terms like smack, crank, dope, blow, or marijuana, and then offer them your ID's, and invite them to view the grow.
Other dude was right, don't fucking 'trust' the police, but always go in prepared for the worst, and hoping for the best.
Personally, I don't think they will ever show no matter how much it stinks... dude will call, and the cops will be like "You said yourself its his medical grow, its not a crime sir, have a nice day" and laugh together at the dude thinking the smell is a sentient satan cloud.....