I too would love to know the definition, according to this poster or the sailplane owner, of what constitutes a suitable context in which the swastika is used and displayed on the aircraft? A white supremist rally like Charlottesville perhaps? A neo-Nazi party picnic perhaps? An airshow sponsored by a Swiss Bank and attended by only Argentinian depositors perhaps?
Because as you said, "because for something like this, a lot of the issue is context." No s**t Sherlock!