Cruz’s PAC first attacked Trump’s family, Trump only responded to the attack.
You can split off responsibility from Cruz if you want, but Donald saw them as coming from Cruz, and I tend to agree with him.
Cruz needs to stand down, and get together with Trump.
Big time.
It was not Cruz's PAC. It was an unaffiliated anti-Trump PAC that no one had ever heard of before, that had raised a total of $20,000, and that got millions of dollars in free publicity by running a Facebook ad with a semi-nude picture of Trump's wife (which she was paid to pose for).
https://www.opensecrets.org/pacs/lookup2.php?cycle=2016&strID=C00594176