Wherever possible, I close the throttle and pull in the clutch when passing by horses - as long as I can give them a wide enough berth. The downside is that you have to coast by a bit quicker (albeit more quietly) as you need to maintain sufficient momentum. I'm not sure whether slowing right down but having twice as many revs going is a better idea.
Genuinely puzzled - never had this quandary when I owned a Japanese bike!
Imagine this for a moment - you are riding a motorcycle that pretty well does as you want it, but when you are faced with other road users, the bike is prone to react unpredictably - it goes onto the pavement, into the face of ongoing traffic, pulls wheelies and tries to land the front wheel on people's heads, etc. I wonder what the chances are of making a motorcycle like that legal, and to cap it off, by law it has the right of way over other traffic.