No, the ACLU does not undermine the war on terror, because the government is over the top on the issue of intruding into personal liberties in the name of safety. I don't like the ACLU any more than any other conservative, but in this case, I trust the government less than the ACLU. The ACLU is doing a valid function, in this case.
Benjamin Franklin is reported to have said, "If we restrict liberty to attain security we will lose them both." I agree. The strength of this nation comes from her emphasis on freedom and opportunity. As soon as we give up any of the freedoms granted by the constitution and its founders, we betray our values and give up our role as the shining city on the hill. Our security lies in convincing all people that we are the greatest nation on earth.