Appeal to gravity

An appeal to gravity is a logical fallacy that occurs if the supposed importance (big impact) or seriousness of a situation makes someone's viewpoint stronger.

The fallacy is an emotional appeal and an informal fallacy.

Form
If discussing someone's ideas:

Explanation
The importance of a decision does not make any one choice of action any better or worse, and the seriousness of a choice of action does not change whether it actually solves a problem.

Appeals to gravity will usually be the person with the serious proposal (which can be just as laughable as the less serious proposals), the person seeking "balance between extremes" (who may manage to find the midpoint between two working solutions), the person "who wants to keep things civil" (and ignore ideas that aren't), or the person who finds some ideas ridiculous. This is because it's easier to criticize how other people discuss the issues than how they solve the issues.

In some cases, addressing issues with relative levity, particularly humor, encourages knowledge, awareness, and discussion of the issue to reach a wider audience (for instance, panel/talk shows and news satire on television). That said however, sometimes not taking things seriously can hurt discourse by making issues seem more or less important than they actually are.