Mutually Assured Destruction
The primary proponent regarding proliferation of WMDs lies in the concept of 'Mutually Assured Destruction' (MAD), where many nations having WMDs ensures that no one dares use them in the first place. Using this as its crux, Israel argues that development of WMDs is net positive and entirely justified.
Moreover, in the Israeli context, any attack on Israel by its regional Arab neighbors would guarantee a serious counter-attack by the former on the latter, further serving to justify Israel's support of MAD.