The minor downside is that it would be illegal, but still a worthwhile act of civil disobedience.
Johnson says we're warming the planet but shouldn't do anything about it because the sun will expand and encompass the earth (ed. note: in hundreds of millions of years at earliest).
We shouldn't spend on climate change because one day the sun will "grow and encompass the earth"—Presidential candidate Gary Johnson in 2011 pic.twitter.com/1ZJSKGN5N6— Channel 4 News (@Channel4News) September 22, 2016
Seems pretty feasible to me - bring a small portable generator (bonus credit if solar-powered) or battery, together with a heat lamp, stand on the sidewalk or street by his yard, and start wilting the grass and whatever other plants are in reach until you get arrested. Even a blowdryer might work, I'm not sure. Nothing that puts out a flame though.
Obviously, Johnson should have no objection to wilting his plants given that the sun will eventually encompass the earth anyway.
If his place is in some gated community, then maybe outside his campaign HQ?
And to be Scrupulously Fair, if Johnson has withdrawn this argument, then don't wilt his plants. His millennial supporters need to know more about his positions though.
Finally, a good point here: continental drift will resolve political problems in the Middle East before the sun moots our response to climate change.