I really like how the conversation is going in this little thread :)))
Speaking from a bit of experience, when you are up close, e.g. kissing, the field of view is very limited, blocked by the other's face, so you would have to rely on the sense of touch and sense of self-movement and body position (scientific name: proprioception) for whatever you do with your hands (and other parts) anyway, so the foggy glasses won't matter. Not to mention after a bit the glasses itself will warm up enough, so the fog won't form there anymore. Glasses can still hinder eyesight due to the sweat and other bodily fluids they come into contact with, though, plus the risk of having them poking where it's not needed.
Also, since the visual data take up a lot of processing power of the brain (avg ~70% daily incoming data), if you cut it off by closing the eyes, you would be able to savour more of the data from other senses and body parts, iykwim, hence the tendency to close/roll-up the eyes during kissing and other stuffs.
What I'm saying is that taking off the glasses or not won't really affect the intimate physical processes. The only downside of taking them off, aside from aesthetics, is that if your eyesight is really bad without them, you won't be able to fully appreciate the view during the intermittent pulling backs for breath.