Unbelievably to me, the thread actually gained more than one person who supported the idea.
Well the majority of Black Bear are not much bigger than a large human male. So if something works well on humans there is a good chance it will work on a black bear. We really have to define if we are talking hunting or self defense. When hunting bears we are going for the vitals. You will need a lot of penetration to reach the vitals on a bear. In a self defense situation you are going for a head or shoulder shot as the vitals will not be visible on a charging bear. With a 45ACP you will want to use FMJ to ensure adequate penetration. Since it is ball shaped to feed in semi-autos it isn't going to leave a very impressive wound channel. It has been said that round nose FMJ bullets leave a wound channel about 70% of their size in actual tissue. In the meantime a HC 44Mag bullet with a massive meplat is going to leave a much better wound channel and also penetrate better. Even a HC 357 load is probably going to leave a larger channel and it will undoubtedly penetrate better. Flatnose HC revolver hunting loads typically leave "full size" wounds. A broad-head arrow would be much more effective than a .45ACP slug. It is going to cut a lot of tissue and cause major hemorrhaging.