This is true, but there is a very simple way around the veto. Acts by individual Houses of Congress are not subject to presidential veto, so instead of a Joint Resolution the House and the Senate could each adopt identical Resolutions of Disavowal. Since such resolutions, joint or separate, have no force of law, both houses, by adopting identical resolutions, would achieve exactly the same moral and political effects (if any) as they would with a joint resolution.
Shane Mage
"This cosmos did none of gods or men make, but it always was and is and shall be: an everlasting fire, kindling in measures and going out in measures."
Herakleitos of Ephesos, fr. 30