I think hindus should preach, their are some who do. And they have every right too. Who gives a crap, what the purposes of non-hindus are when preaching. If you believe in your faith as the truth, then you want to spread the truth to others. Hindus believe the same. It's only indian exclusivism, that keeps use from genuinely spreading our faith. So indians think that non-indians wouldn't know how to practice hinduism. That it's better left to indians, which is false.
I think the Swaminarayan faith is very different in that reguard, we have an obligation to spread the name of Lord Swaminarayan far and wide and we take pride in that, if it's the truth then you shouldn't be afraid to tell it. There's nothing wrong with seeking converts to Hinduism, arguing about what "infidels" do is meaningless and a waste of time. We should be focusing on our mission. Some hindus are too introverted to the point of self-destruction. There's no crime in spreading our faith, we have the right and obligation upon us.