they're violating my Constitutional rights when I try to cast a ballot and tell me I can't?
I've been in that situation more than once. Once I arrived in my new state of residence 5 days before election day. I think same-day registration is a bad idea. I could easily have voted in my former state of residence during early voting or voting by mail. Casting two votes in a national election is probably not a good thing, if we believe in representative democracy (and not Chicago-style democracy: vote early, vote often, and vote in pencil so we can fix your mistakes.)
I figure that's like the unconstitutionality of restrictions on free speech, things like "Kill the president! Now!" while attending a fundraiser while Obama's speaking. Or yelling "Run! He's got a gun and is going to kill everybody!" at a baseball game. Or restrictions on freedom of religion that involves, oh, human sacrifice.
We can discuss the Texas restrictions, accuracy of estimates, etc., etc., without hyperbole.