You cannot have a "simple philosophy" because philosophy is not simple. Why are philosophers so difficult to read? Not to mention that their works are typically tomes and each tome ties to the next so that to grasp the entirety of one Thinker every single work must be read. It would probably behoove one to read said Thinker's personal letters and journals as well.
This is because philosophy must be stacked on top of itself. Each little piece must have a premise that no one can dispute is the basis and build up from there. Not only is it difficult to find that beginning premise but the constructions that are then laid on that base must be aligned perfectly to it else your philosophy begins to tilt to one side or seem to have pieces missing like a mental game of Jenga.
Now if the venue is appropriate, feel free to call out our simple friend on his/her philosophy. If you know me, you'll understand that almost any venue is appropriate. Make sure that s/he can really back up this claim to simplicity. This is, of course, impossible and will become evident very quickly. Then just point out this fact and proceed to allow him/her to build that Jenga tower.
Be gentle. But firm. We have no time for slackers. Make everyone think.