Your friend is totally clueless about cats. My daughter was going to adopted a cat that was already declawed and I called a no kill cat shelter and I was told they have a hard time getting people to adopt declawed cats b/c they bite . If you take away a cat only 'weapon' to defend it he is going to use the only thing he has left and that it teeth. I would rather get
scratch by a cat than get bitten. If your cat got outside by mistake it's not going to have any way escape if he can't climb a tree or fence. I used a spray bottle filled with water and if my cat was even thinking of doing something wrong I just had to pick up the bottle and he would take off. It's very cruel to put your cat through unnecessary pain . This web site said a declawed cat may not use a littler box . Cats use their claws to help them land better , the claws help them keep their balance.