The name "semicolon" is not politically incorrect (yes, I'm aware the above was probably meant as a joke). The semicolon is in fact a weaker punctuation mark than a colon, or indeed a period; it is often useful in cases where a comma would be not enough, but a period would be too much. This is readily apparent if you read the sentence out loud in your head: for a comma, you pause for a certain amount of time x > 0. For a period, you pause for a longer amount of time y > x. For a semicolon, you generally pause for an intermediate amount of time s, y > s > x. ∴, assuming that relative length of pause indicates relative strength of punctuation, the semicolon is betwixt the comma and the period in strength.
In addition, the comma requires a conjunction to join two clauses together, whereas the period ends a sentence entirely. The two clauses separated by a semicolon are generally not as related as two clauses separated by a comma, so they don't get a word to describe their relationship; the semicolon'd clauses are, however, not as unrelated as two separate sentences often are.
The semicolon is, incidentally, my favorite punctuation mark.