I could be wrong but I think the thrust of this is that Cruz has lost. For his supporters to continue the divisive rhetoric (both sides btw) will not help the country in the end. And that debate, Cruz or Trump, ended when Cruz was eliminated from reaching 1237.
It’s not like they’re both still in the race anymore than Bush, Walker, Perry, Paul, Carson, Fiorina, Huckabee, Christie, and others are still in the race. But Cruz and Kasich won’t admit they’ve lost and drop out. Instead they fight to find a way to overturn the will of the people. I think Jim probably doesn’t want to help them achieve that.
Makes perfect sense, and should have been explained this rationally.