1. There is a long history of purely empty hand arts in China and on Okinawa that developed independently of any weapons.
I'm sure your phraseology isn't saying what you meant there. I would maintain that no (non-sport) empty-handed art developed in isolation as, to be effective, they have to take the prescence of weapons into account.
2. The fact that kobudo and karate have some similar moves and dynamics does not mean that either developed from the other.
True. I would still be very surprised if there was no linkage between the armed and unarmed styles tho'. It would be very difficult to investigate and prove one way or the other so we are left with our impressions and our opinions based upon what we observe (and some common sense).
3. There are weapons ryu that do not use karate type stances and the dynamics of which are unique (Yamani ryu).
Quite so. I don't know the ins-and-outs of Yamani ryu so I can't speak to that specifically. However, the postures in MJER iai have similarities to some karate stances but are not the same because, after all, we are dealing with three foot of steel in our hands.
4. Some of you sound like you are trying to learn to do sword using karate stances and dynamics. That is incorrect and misleading. Kenjutsu and karate have almost NOTHING to do with each other. Find a real sword school.
<snip harshly worded points>
I agree with what you say about how trying to 'force' a swordart into a karate mould would deform it unreasonably. However, perhaps it could've been phrased in a touch less inflammatory way? Disagreement doesn't have to be a conflict and a counter-point discourse can still be courteous.
9. My suspicion here is that, in some cases, this whole theory is an effort by some to find an excuse for doing karate kata with weapons or vice versa and for simplifying things to suit them. Kobudo and karate are very different arts. Just because a typist and a concert pianist sit alike and use the same motions does not mean that Mary Lou Headlights out in the office will be playing Mozart concertos at home tonight.
I concur with your last point there and it's a good way of illustrating that similarity does not necessarily connotate a causal relationship.
Are we not in danger of forgetting here that the 'martial artists' of the time when 'our' arts were developing were soldiers and thus did not study iaido, kenjutsu, karate etc as seperate, compartmentalised, entities? The list of arts that a samurai was expected to learn was quite extensive last time I looked and formed a suite of techniques. What was used where and when was situationally dependant, just like the arts studied by our WMA compatriots. That is one reason why I do not think it beyond the realms of possibility that motions, postures and actions were codified to an extent to be present in more than one of the arts.