ive had my horse for around 7yrs now and love him to bits. He is 18yr old STB geld, now fully retired..problem is he is turning aggresive towards everyone. He has never previously shown aggresion towards me until recently (nothing major just biting, threatening and ears pinned back). He HATES men with a passion. I went away recently and had horsey friends fill my horses waters up etc. He knows these people and they have only ever been nice and friendly to him however everyday the visited he would charge full pelt at them chasing the from the paddock and spinning to kick them. Luckily he didnt manage to get them but im at a loss with his attitude. He is very bossy to other horses too. He was a bucker under saddle and had chiros etc to see him but they said he was fine. Where to go from here? Sadly the thought of having him PTS has crossed my mind but id like to hear some suggestions that may help first. Rehoming him is out of the question as he will hurt someone.