This quote by Cyril Connolly suggests that although vulgarity may not be pleasant, it is a vital part of life. Simply as garlic is an important active ingredient in a salad, indecency is an important part of life. It is a reminder that life is not constantly best which there are some undesirable aspects to it. Indecency can be seen as a reminder that life is not always simple and that there are some hard and unpleasant minutes. It can also be seen as a tip that life is unforeseeable and that we need to not take anything for given. In this method, vulgarity can be seen as a pointer to appreciate the excellent minutes in life and to be gotten ready for the bad.
"Life is life - whether in a cat, or dog or man. There is no difference there between a cat or a man. The idea of difference is a human conception for man's own advantage"