I hate my Dad and feel so guilty

Dad was diagnosed with dementia about a year ago. What a year! Aggressive, stubborn and impossible to help him. Determined to stay in his own isolated home, and being so vile to the family. He always was a selfish, stubborn man, so I find it really hard when soppy people talk about 'your loved one'. I feel so guilty that I can truly say I loathe my father, and only need to hear his voice on the phone to get my nerves on edge. He has gone from physically attacking me when I tried to help, to constantly phoning me up, demanding that I come instantly as he's not well. The awful thing is that I believe that he still has some control over his behaviour - the dementia has changed some things, but when he really needs to, he seems to manage. Dreading the future, because I know that I will carry on trying to help him as much as I can, but hate the person I am turning into.