Unintended consequences?

Does Citizens United compel public sector employees to support corporate political campaigning? One Harvard professor thinks so. Most public sector employees are required to make contributions to a pension plan. Many public sector pension trustees make investment decisions in the private sector in corporate securities. The problem is Citizens United permits corporations to make political expenditures from the corporate treasury. Essentially public sector employees are compelled to finance private corporate political expenditures with no mechanism for opting out. Unions, of course, cannot use employee dues money for political expenditures if the dues payer objects. The professor suggests this compelled financing of corporate political speech violates the public sector pension contributors' First Amendment rights. Intereting argument.