The dangerous thing about the deal with India is that it means that the US doesn't have the high ground. If you allow India nuclear weapons then how can you turn around and claim that Iran is not allowed the same privilege? While as you say India is unlikely to give up their weapons, when you make it easy for them it only undermines your stated goals with other (more odious) countries.

On the other hand, it may be that offering different levels of trust to non-odious states than to odious ones would motivate governments to aim for the former status. (I don't know that this would work, but it's not clear to me that treating states as interchangeable black boxes necessarily works all that well either, even in principle.)

If you allow India nuclear weapons then how can you turn around and claim that Iran is not allowed the same privilege?

As opposed to "allowing" the UK, France, PRC, and Russia? Is there a particular fairness in the system of "anybody who developed them soon enough to allowed to have them and develop new ones, but not anyone else?" Is it even enforceable?

Nope, it isn't fair. Taking this line of reasoning to its logical conclusion we end up with a world where almost everyone has nuclear weapons and things don't blow up only because of multi-way mutually assured destruction. Probably after a couple of accidents everyone will grow up a bit.

Of course I only point out problems, I don't have a solution. But certainly randomly invading countries is not a long-term viable approach.

"If you allow India..."
India is an independent nation.Who is there to "allow" sanction this thing or that thing?Nuclear deal is a two-way affair.You destroy your weapons....

You want India to give up their nukes? Easy, get the Chinese to give up theirs, which they will gladly do once the Russians give up theirs, and they are just anxiously awaiting for the Americans to give up theirs first.

Iran is not getting nukes because India has them. Iran is trying to get them because they have several thousand American troops on their eastern border in Afghanistan, several thousand American troops to their west in Iraq, surrounded by several American naval bases - and off over the horizon the Israelis have several hundred warheads. Under these conditions, the Iranians would be suicidal to not even try for such weapons. If you want Iran to abandon it's pursuit of such weapons, address some of these concerns.