My responses:
A) Not immoral but cruel and mostly unnecessary IMO.

B) To some extent yes. If you irritate a polyp it reacts which means it has the ability to sense its surroundings and react. Additionally, irritating that polyp will cause the whole colony to react suggesting a central nervous system. Remember corals are animals and not plants so cutting a tree down is quite different.

C) Killing to thin back should be a last resort. Many reefers would gladly buy, trade or take most (if not all) corals off your your hands. Newbies especially.