It is often easy to take advantage of someone by suggesting that certain actions are good or bad by taking a moral or ethical position whether truly felt or not, because emotions overcome reason. Similarly religious grounds have been given by powerful people to gain advantage, ignoring the disadvantages which inevitably arrive and hit them almost totally unprepared. What is good for someone can be bad for someone else so these terms can depend on one’s viewpoint. Instead of a simplistic good vs. bad perspective it’s better to measure situations or ideas both from immediate advantages as well as long term costs and benefits, grounded in reason instead of emotion.
Often, taking advantage of the short term perspective results in long term disadvantages. Short term actions can stem from impulsive, greedy motives.
While short term thinking and acting isn’t always negative, conflicts may arise making it difficult to weigh factors, and make decisions. On a large enough time scale, short term thinking often has negative effects on overall society. However, a blind adherence to very long term goals leads to unreasoning inertia that makes needed or even opportune social or economic changes dreadfully slow, to the detriment of the overall project.
So how short is short term and how long is long term? In general, a three point rule offers a reasonable guide for thinking and acting. When we look at societal structure, successful families invest their energy on themselves, their children and grandchildren. We see great happiness among families thus organized in terms of generations, with an eye toward the future, and unhappiness among families that cannot give an endowment to second and third generations. In western culture most families are integrated only to the second generation, and we see disharmony and unhappiness within families. If enough families give insufficient thought to future generations, it will render society dysfunctional.
But if families accrue resources to provide for more than three generations, then we get into the state of rich getting richer and poor getting poorer. As a result any broad societal change will be harder to achieve. However, if families only invest in themselves then one will see a decline in population or dysfunctional next generations as is evident in the current world.
The three point rule, or three generations ahead thinking seems to be a fair rule to differentiate between short term advantages vs long term benefits which can be viewed as bad vs. good. If it decimates your family or financial situation or society, then no matter how good the benefits are for oneself today, it's probably not a worthwhile idea in the long run.