Why is it “bad behavior” to try to win an election?
Why do you feel Kasich and Cruz are obligated to both campaign in Indiana and split the Trump opposition vote? What rule says they have to do that?
You can be upset that this hurts Trump’s chances of winning the state, but to say there is something morally wrong with this makes no sense at all. This is smart strategy on their part. It’s a campaign tactic that on a moral level is purely neutral.
Trump is campaigning strongly against the rigged, corrupt system. What Cruz and Kasich are doing substantiates that claim. A more honest, open approach would be for one to drop out and decide to either endorse or not endorse someone else.