Cruz went after Trump for his liberal record. I see nothing at all wrong with that. That is the point of a primary.
By the way, is Cruz involved in the attack on Phyllis Schlafly? Her Conservative record & identification is absolutely flawless. But Cruz is being accused of involvement with those trying to take her organization away from her. (I really do not want to believe that he would stoop to involvement in that; but he has been openly accused of involvement!)