Can I get excused from a contract or have grounds to sue based on on disagreement with the contractor's public political bias?

I don't think you have a case.  You didn't ask about ATT's politics before entering into the contracts, it didn't lie to you and had no duty to disclose its politics in negotiating a normal commercial contract.  Even now, while you state that you didn't know about the ATT President's poitics before entering into the contracts, for fall short of claiming that you wouldn't have entered them if you had  known.  Also, the politics of ATT's President, with whom you have no contract, is not necessarily the politics of the corporation, nor does the fact that you disagree with the politics of ATT's president mean that the money you pay ATT or one of its subsidiaries is being spent on any political purpose.  All that being said, my gut is that a court might feel some sympathy for your position if the president had expressed sympathy for some really far out political group, like the American Nazi Party.