This has nothing to do with the merits of the the boycott, divestment and sanctions (BDS) or its opposition. Requiring contractors and employees to pledge that they will not support the BDS movement contravenes core free speech values. Ironically, many of these same politicians support corporate free speech rights in cases like Citizen’s United but want punish companies who disagree with them to be punished.
I have no problem with private boycott calls, which is an exercise of free speech. People have a right to speak through their purchases when a company takes official positions like this on major controversies. Thus, politicians have called for people to stop buying the ice cream and New York City Mayor Bill de Blasio, said he would be forgoing “Cherry Garcia for a while.”
An actual state boycott could raise serious constitutional questions in interfering with interstate commerce and free speech. However, states have a right to be market participants.