I have always thought of moderation as a good thing, but John Stuart Mill is willing to take the contrary position and argue against moderation if moderation is imposed by someone else. Here is what he says in On Liberty, Chapter III: “Of Individuality, as One of the Elements of Well-Being,” paragraph 15:
There is one characteristic of the present direction of public opinion, peculiarly calculated to make it intolerant of any marked demonstration of individuality. The general average of mankind are not only moderate in intellect, but also moderate in inclinations: they have no tastes or wishes strong enough to incline them to do anything unusual, and they consequently do not understand those who have, and class all such with the wild and intemperate whom they are accustomed to look down upon. Now, in addition to this fact which is general, we have only to suppose that a strong movement has set in towards the improvement of morals, and it is evident what we have to expect. In these days such a movement has set in; much has actually been effected in the way of increased regularity of conduct, and discouragement of excesses; and there is a philanthropic spirit abroad, for the exercise of which there is no more inviting field than the moral and prudential improvement of our fellow-creatures. These tendencies of the times cause the public to be more disposed than at most former periods to prescribe general rules of conduct, and endeavour to make every one conform to the approved standard. And that standard, express or tacit, is to desire nothing strongly. Its ideal of character is to be without any marked character; to maim by compression, like a Chinese lady’s foot, every part of human nature which stands out prominently, and tends to make the person markedly dissimilar in outline to commonplace humanity.