Argumentum ad populum

As per Wikipedia,

In logic, an argumentum ad populum (Latin for “appeal to the people”) is a fallacious argument that concludes a proposition to be true because many or most people believe it. In other words, the basic idea of the argument is: “If many believe so, it is so.”

Some simple examples of this fallacy are:

• Everyone’s doing it.
• In a court of law, the jury vote by majority; therefore they will always make the correct decision.

Some other important issues that suffer from argumentum ad populum:

• A politician charged with provoking riots claims that majority of people have voted him back to power; so this charge against him is false.
• XYZ religion is followed by millions; therefore all its claims are true.
• Chemical castration for rapists is the right punishment because the majority wants it as a law.
• A government is elected democratically and by vote of majority; therefore all its policies represent the people.

Such arguments may sound persuasive but can be fallacious at the same time. One could claim that smoking is a healthy pastime, since millions of people do it. Governemnts, religious clergy, godmen and other groups try to suppress dissenting and unpopular ideas normally resort to such arguments to persuade people against these ideas.

In fact, centuries ago, almost everyone used to believe that “the Earth is flat”. Does that mean the Earth was actually flat and that it has become round now because most people believe that now?

Therefore, a clear logical analysis of important arguments is necessary to understand whether we are believing an argument because it really true or because we see majority agreeing with it?

Do you know any other prevalent ideas that are assumed to be true just because many people believe it to be true?