It’s interesting how commonly-used aphorisms eventually become used in a context opposite to their actual meaning. One particularly egregious example is the phrase “it’s just a few bad apples,” frequently used to defend a group or organization from the actions of a few. Variations of that theme are a staple of modern political rhetoric.
The correct aphorism, which you have doubtlessly heard a few times in your life, goes “one bad apple spoils the barrel.” The reason? Because when an apple over-ripens and spoils, it produces ethylene, which acts as a ripening agent and causes the other apples in the container to go bad as well.
So when you try to defend a group by referencing the “bad apples” analogy, you are in fact supporting the argument that the organization is rotten.
Now how about “Jack of all trades, master of none?” Usually used disparagingly toward somebody who has many skills, but is not outstanding in any specific one, its traditional usage is less so. A Jack-of-all-trades would be a generalist rather than a specialist, sometimes called a polymath or a “Renaissance man.” Leonardo da Vinci and a number of ancient Greek philosophers come to mind. Would you disparage any of the classical great minds, a great many of which dabbled in many areas instead of focusing on a single field? I doubt it.
The “master of none” part seems to be a more recent addition to the adage, and other, longer versions of the saying exist.
“Jack of all trades, master of none,
Oftimes better than a master of one”
Wikipedia has a list of interesting variants from other languages, as well as a bit on the history of the phrase.
I’m not as knowledgeable of the history of “curiosity killed the cat,” but a well-known retort to it is “and satisfaction brought it back.” It seems that it could originate from a play performed by The Lord Chamberlain’s Men, a group including William Shakespeare, where the phrase “care’ll kill a Cat” appears. (“Care” being defined as “worry” or “sorrow” in this context.) It shows up again in Much Ado About Nothing.