Churchill himself told his war Cabinet July 10, 1940 that the threat of Sea Lion being launched could be ignored because it was so obviously suicidal that no one could ever seriously consider launching it.
A month earlier he was convinced that an invasion was going to happen and that he would likely die during it. He had also been the first member of the Cabinet to suggest that an invasion was possible in the first place, this back in 1939. Preparations for a possible invasion (which were quite extensive: lines of fortifications were built all over the place and just about every Channel beach had, at least, a pillbox overlooking it. You think governments spend massive amounts of money on things like that just for the sheer hell of it?) and the general mobilisation of the population had both gone very well, and there are only a few months of the year in which an invasion of Britain is ever anything more than monstrously risky because the Channel is a very dangerous body of water. The optimistic view (which turned out to be correct) by the early Summer of 1940 was that if there were no signs of
imminent invasion, then the bullet would have been dodged as by the next time an invasion was physically plausible, then the fortification of Britain and the mobilisation and arming of its population would have reached the point where an invasion could be repulsed with confidence. This was not the case in the first half of 1940 and it is worth noting that even a completely catastrophic invasion would have completely devastated a substantial part of the South of England, particularly Kent and Sussex. The general view of the British public throughout most of 1940 was that an invasion was probably going to happen, but that if it did it would be unsuccessful: the will to fight was extraordinary, a rather relevant point given the nasty and stupid argument of yours that kicked all of this off.
Also, while Barbarossa had a 0% chance of occurring successfully, the idea of Nazi Germany raising it’s flag over the Kremlin didn’t. Of course, that’s not true of Sea Lion.
The critical difference is that Stalin was convinced that his new best friend would not invade, refused to prepare for an invasion and had any intelligence officer that suggested that an invasion was imminent shot. Had the Soviet Union been as prepared in 1941 as Britain was by the end of 1940, then there is no way that the invasion force would have penetrated as far into the Soviet Union as it actually did and millions of lives would have been saved.
Even the most generous Historian analysis’ of Sea Lion don’t even see Germany reaching London.
Real historians (and I ought to know as I
am one) generally don't concern themselves with hypotheticals, not professionally anyway. The classic view is that the Historian should be concerned to discover only 'what actually happened' (and the reasons for this), not what might have been, and to the extent that this position has been challenged it is only because of the view that it is often not possible to know 'what actually happened' with iron certainty.
A famous Sandhurst wargame (designed largely by the great Paddy Griffith) conducted in 1974 concluded that an invasion in September 1940 would have ended in a catastrophic defeat for the invaders, and this is about as far as we can go in terms of certainties: a well-designed and meticulously executed simulation. Does it supply us with facts, as such? No, merely probabilities. Does it supply us with the full range of probabilities in response to all possible events during 1940? Certainly not and it was not designed to do so. Does the likelihood that an invasion would have been comprehensively repulsed mean that there was no threat posed to Britain or to its government by an invasion? The suggestion is self-evidently absurd. Does the likelihood that an invasion would have been comprehensively repulsed due to well-planned defences and a highly motivated population suggest that the British people of the time were somehow lacking in martial spirit or 'toughness' or whatever other nonsense you were drooling on about in the other thread? Only if you are hallucinating.