I think you understood my comment as almost the opposite of what I wanted to say. My point is that if US security concerns were a valid reason to oppose Soviet

I think you understood my comment as almost the opposite of what I wanted to say. My point is that if US security concerns were a valid reason to oppose Soviet missiles in Cuba, then by the same standard Russian security concerns are - or at least can be - a valid reason to oppose an Ukrainian NATO membership or at least an unrestricted placement of NATO assets in Ukraine. Or the other way around, you can not easily argue that the USA can decide whether or not Cuba can have missiles and at the same time argue that Russia has absolutely no say in what kind of NATO assets end up in Ukraine. And to be even more specific, I am not arguing that both can not be true at the same time, they are not identical situations and all the small differences might add up and make a difference. But this is something one has to make a case for, Ukraine is a sovereign state and decides for itself whether or not it joins NATO doesn't cut it, at least in my opinion. Or pick the other side and argue that Cuba should have been allowed to host missiles and the USA was wrong preventing this, which probably will imply that Russia or China should be allowed to place missiles in Cuba today.