If anyone has people like this in your life, the Bible gives you a little ammo for changing their mind. First of all, mankind was given stewardship over the Earth. God expects people to not trash the place.

Secondly, Jesus was quite emphatic that no one would know the day & time of his return. He did say there would be warning signs, but also said it would still be a surprise. If someone wants to destroy the world in order to push for the Second Coming, then they're on the verge of being a false prophet as described by Christ. Not to mention: why take the risk when this might not be the time of his return?

I'm personally not a believer now, but I was raised in a very conservative Christian family. These arguments sometimes have an effect on my friends and family still in the church.