If you are aware of the justification, then you must also be aware that if the airlines did not run this policy, and flew with empty seats, then the cost of seats would be exponentially higher.
Think about it - no airline is going to say "I know, let's run a route, but let's be really awkward and overbook and then compensate people, that's a really excellent financial model, and it will really annoy our passengers, and make sure our ground crew get loads of abuse - what's not to like?"
The reality is "If we overbook on certain routes, we are guaranteed that all our flights run full, which makes for minimum running costs and maximum profit, which is why we are in business. The downside is that overbooking passengers will be annoyed, but hopefully we can offset that with re-scheduling and financial compensations where possible. It makes for some awkward scenes, but it is economically viable to work this way, because if we ran with empty seats, we would have to increase prices, which would lead to more empty seats - no-one wins."
P.S. "Someone called jd_1984 may accuse us of being greedy and immoral, but we are a business, and we work the most efficient way we can.