My attitude toward the idea of the "Third Temple" being built in Jerusalem, as some have discussed (for both good and bad reasons), is actually quite simple.
If Jews want to build a Third Temple as a way to increase their piety, humility and worship of God, then what is the harm in that? Honoring and worshipping God is only good.
But if the Jews want to build a Third Temple to make a political statement, to stick their finger in some other religion's eye, to try to manipulate divine events to solve everyday political problems, or at the behest of nutty Christians who are nihilistic in their interpretation of scripture, then how stupid would THAT be? To build a Third Temple for any reason than increasing humility, piety and worship of God would be the height of folly.
So if the intentions are totally pure (as the priests must be) then knock yourselves out and build a Third Temple with my blessings. Though I wonder why synagogues are not packed to the rafters around entire country if people are thirsting for greater spirituality. Nonetheless, if you really think that the Third Temple would bring a revival of Jewish piety and faith, then obviously that serves God and it is good.
But if the intentions are not totally pure, check out what happens to places of worship that are impure, as are well documented in the Torah. (Hint: If Christians cite that bad things will be fulfilled when the Third Temple is built, then they are correctly interpreting that if the intentions were impure and the Temple is built, that's not a good thing, and you don't need to be a mystical prophet to figure that out.) I mean, remember, someone died when he touched the Ark while trying to keep it from falling off the transport cart. It's God's way 100 percent or the highway.