That's a remarkably lame argument. If something is a conflict for a significant number of people who would otherwise attend your event, then trying to avoid that conflict is accommodating those people, not whatever thing it is that is responsible for the conflicting event.

For instance, if a significant number of US PyCon attendees were ardent chess players, then avoiding scheduling PyCon to overlap with the US Open chess tournament would not be pandering to chess. It would simply be recognizing that PyCon attendees have lives outside of PyCon, and when a particular date is bad for many of them, it makes sense to try to avoid scheduling PyCon on that date.

Furthermore, if it were a conflict with chess, I doubt you would have posted that there are chess tournaments every weekend and since PyCon can't avoid them all, it should not try to avoid any of them. You would recognize the utter idiocy of not distinguishing between major national tournaments that people make significant long-term attendance plans for (such as the US Open), and, say, weekly quads at the local chess club.

ergo the innuendo of second year in a row