Trump didn’t say Kasich couldn’t do it. He said if Kasich lies, they’ll sue. About damn time, so many lies anymore and no one does anything. Great example, McDaniel in MS, they said he was with KKK, that he was behind the leaked photo of Cochran’s bedridden wife, etc. And the Cochran campaign never had to answer for it.
Free speech doesn’t mean you can defame the opponent.
If Kasich engages in libel and slander, then yes Trump should sue, so if that was the point he was trying to make then I get it. I would really like to see the ad, although Kasich is such a creepy dude, I feel dirty defending him.