NEW YORK — House Speaker Mike Johnson, the Louisiana Republican, held a press conference on the steps of Columbia University above an encampment where demonstrators demanding the school divest itself from Israel-linked businesses have occupied since last week.The speaker blasted university leaders for permitting “mob rule” and intimidation tactics “overtake” the Founding Fathers’ ideals of freedom of speech, freedom of religion and “the free exchange of ideas.” Columbia President Minouche Shafik was seen walking away from…