I like the answers already, but I think there's a slightly different angle too.
My personal opinion is that a large part of the reason it often gets a negative response is because it's often brought up in the context of certain "itneresting" individuals ascribing some negative trait (often imaginary) to the skeptical movement, with the implication that most skeptics have this flaw. Not naming names, or anything. It's easier to slander a non-existent group than a real person.
Sure, there's a skeptical movement. Of course it has a zillion different goals, and is composed of thousands of groups which have a nodding acquaintance at best, so talking of "the skeptical movement" is of limited utility at best (as opposed to talking about a more concrete and cohesive group.)
I completely agree with your first and second paragraphs in letter and your third in spirit. It has never been my contention that there is a "One, Holy, and Apostolic Skeptical Movement", or, as it is more often called the "Organized Skeptical Movement". However, I find the seeming cognitive disconnect between there being social groupings of skeptics drawn together by their skepticism and there being social movements based on skepticism (which is what I mean by "skeptical movements") very frustrating. I have given the examples of the Civil Rights Movement and the Reformation as vast social movements that resemble that set of all skeptical movements in that many disparate societies and organization that were conceptually related by a set of common goals.
However, there have been many movements throughout human history. Looking just within Christianity, which itself was collection of social movements conceptually untied by their belief in Jesus Christ as their Lord and Savior before it received the official sanction of the Roman Empire, there are a multitude social movements the individual communities of which were conceptually united by shared goals but that did not necessarily agree on details of how to achieve them. Early hermetic and monastic movements strove to achieve salvation by renouncing worldly pleasures. The Reformation, the Restoration, and the Great Awakenings were all movements aimed at reforming, restoring, or revive the Church to its former glory and purity. However, no-one would claim that since there were many hermits and monastic communities with differing opinions on how best to achieve salvation, hermeticism or monasticism did not exist. Similarly, no-one would claim that, because the Reformation, the Restoration, and the Great Awakenings gave rise to many feuding denominations, those events never happened. Nonetheless, it seems that self-identified skeptics seem to be claiming just that about the relationship that individual skeptical societies and organizations bear to the abstracted "skeptical movement": since these skeptical societies and organizations are disparate in some of their goals, a decentralized movement of autocephalous skeptical societies and organization does not exist.
How does the Protestantism of Luther, Calvin, Sattler,
et alia and their goal to reform the Catholic Church differ so much from the skepticism of Randi, Dawkins, Shermer,
et alia and their goal to improve society through critical thinking and scientific research that the former constituted the Reformation and the latter doesn't constitute a skeptical movement (or skeptical movements)?