What counts are results in terms of more stability and security, not ideological purity in the cause of disarmament. A world free of nuclear weapons, however desirable, is not achievable now or in the foreseeable future. Therefore, the question for the foreseeable future and perhaps beyond is one of management, not of final disposal. Unilateralism now tempts both protagonists of the Cold War, albeit for different reasons. This is a danger.
Unilateral action is by definition reversible.
It is also often unverifiable. Its general effect is to corrode trust in the efficacy of multilateral action and institutions. Exhibit B is the continuing effort to modify the ABM treaty. Still, it has to be admitted that there were and are some valid concerns with the CTBT, such as verifiability of possible violations of the treaty through low-yield explosions given rapidly changing technology. One certainly hopes that these concerns can be addressed so that the US would ratify, and the CTBT would become a dynamic instrument in support of nuclear disarmament and non-proliferation.