absolutely not. My horse is turned out all day long. He sleeps in his stall but in summer he's out 24/7 weather permitting
Honestly it should make for a calmer happier horse. Theres no reason for stubborness to ensue or any kind of aggression. They're out in a more natural environment, so they are so much more willing to work
My horse comes to me, Stand perfectly still wen I come to get him from the pasture, doesnt fight, has never bucked, and is always very calm and is almost bomb proof. I think that his natural time really allows him to be happy to come to work. He actually opens his mouth to get his bit...he'll pick it up off the ground its adorable.
I think horses with plenty of pasture time are overall happier to come work and are generaly calmer. I've seen no problems arise from it. He wasnt always turned out all the time, but the improvement came with it. I'd highly reccomend it =D I like the idea of them feeling freer