They are trying to say, "I'm correct about everything and you should die," because that is what they are always trying to say.

But there's a kernel of truth in the statement if you use very broad definitions.
Right = Conservative = Keeping things the way they are.
Left = "Progress" = Changing things.

The right builds and maintains institutions. This is hard, it takes effort to assemble things in an orderly way. As opposed to the chaos of submitting to base desires and spending all your time obsessed with drugs and sex. If you want to wax philosophical about it, the left-wing is the omnipresent threat of the heat death of civilization. All things that can be built will eventually decay, so it is true that reality has a left-wing bias: entropy.

Or if you want to be less pessimistic about it, they're braindead enough to think "conservative" means a complete lack of change. So any shift in anything is left-wing. Every way your life is different now than it was 5 years ago is "left-wing." Though I suppose there's an argument to be made that novelty-seeking is a more left-wing trait.