That is also a weak strategy, given that polling shows them close in the upcoming Iowa caucuses and the NH primary.
Cruz needs to avoid direct confrontation with Trump, because it could well damage Cruz's chances more than Trumps, and it weakens whichever one of them may end up in the general election.
A better strategy for Cruz would be to simply say, I can understand why Trump did what he did, but in doing so he denied the American public a chance to hear all of the candidates, and share his views. And then focus the debate on issues and just ignore the fact that Trump wasn't there.
Or, Cruz could have taken a bold choice and joined with Trump to sink the Thursday debate - immediately making it the undercard debate. Doing so would help put the MSM back in their place - as news reporters not activists.
Nobody watching the candidates at this point thinks Trump has any problem in debates with the other candidates. In the last round both Cruz and Trump showed that they can debate well. Rubio looked pretty good too. The rest looked and sounded like amateurs in comparison.
That would definitely be a bad move for him.
Cruz needs the debate, Trump has decided he doesnt because of recent poll numbers.
Plus, Trump is smearing Cruz publicly (just a Canadian) just like he has in past Kelly(just a Bimbo) . So Cruz taking Trump's side in Trump quitting the debate makes little sense.