NOPE it is NOT "their duty to find the source and eliminate it". all they have to do is to buy from your competitor instead of you.

Erik,
Perhaps you have a problem of evaluating everything either as black or white while many times truth lies somewhere in the gray region. All you have to do is completely reading my message. I said if someone installs a Power Relay running a DC motor without a snubber, protection diode or any other precaution to reduce EMI ,it is his fault if my board doesn't work properly. There are some EMI sources that can/must be eliminated at its source.
And of course there is a limit to certain amount of EMI that a design can withstand and it's matter of cost/performance not proper/improper design.