Yes, the veto power is critical on the UN Security Council, even as it pertains to nuclear proliferation, because otherwise the countries are effectively giving up their sovereignty to the United Nations. This would be particularly problematic when it comes to nuclear weapons, because another nation dictating nuclear policy to another could literally destroy that country.
Any deal that can be held hostage to the interest of a single party will prove very fragile indeed. What is worse, two members of the Security Council, China and Russia, not only are known for their own flagrant disregard of human rights, but support of states that contribute to global instability. Parties with a vested interest in seeing unstable states maintain nuclear arms are certain to abuse the Security Council veto for strategic purposes. More of the world wants nuclear proliferation to end, than for it to perpetuate. In this case, the majority is right, and humanity would benefit from majority rule.