Inspired by the ignorance of Bill Nye the science guy...
Some things I wish everyone know about philosophy:
(1) Descartes' "I think, therefore I am" does not imply that your existence depends upon your thinking. It is merely intended to show that a thinker cannot coherently doubt their own existence.
(2) People are often quite bad at reasoning. Logic, a component of philosophy, can help with this. (Supplementing this with an understanding of statistical and probabilistic reasoning is still important, though!)
(3) When philosophers raise outlandish-seeming questions ("What is your basis for expecting the sun to rise tomorrow? Or for expecting the future to resemble the past?") it is generally not because we think them unanswerable, or that we think the outlandish possibilities being hinted at are credible, but rather that consideration of the question can give rise to important insights, e.g. into the nature of our everyday knowledge. So to mock philosophers for their thought experiments is as silly as mocking Einstein for (supposedly) thinking that you could ride on a ray of light. It merely reveals that you have missed the point.
(4) Many important intellectual questions (including, e.g., fundamental moral and epistemological issues) do not concern empirical happenstance, and so cannot be answered by the methods of science. Different methods are needed if we are to make any progress in thinking about them. This sort of thinking is what philosophy is all about. If you dismiss it, you are effectively giving up on rational thought about non-empirical matters.
(5) Philosophy is inescapable, in the sense that wholesale dismissals of it tend to be self-defeating. If you dismiss it as worthless, you’re making a claim in ethics or value theory, which are sub-fields of philosophy. If you think it’s an unreliable source of knowledge, that’s epistemology. Either way, you must engage in philosophical reasoning and argument in order to (non-dogmatically) assess the value of philosophy.
(6) While philosophy is difficult, and often controversial, it does not follow that it is "all just a matter of opinion". Some opinions are more reasonable, or better grounded, than others. Even if it turns out that there are multiple internally-coherent ways to think about the world, given the evidence available to us, our initial thoughts on a topic tend to be so riddled by implicit inconsistencies that philosophical thinking can allow us, individually, to make a great deal of progress in improving the coherence of our world views.
(7) Philosophy, as a collective enterprise and academic discipline, makes progress by identifying and resolving common inconsistencies, clarifying what the implications of various positions really are, or which claims do (or don't) rationally support each other.