That said, you really can't fight City Hall and faux moral outrage. They live for an argument, and I, for one, don't want to try to win a poo-flinging contest.
What to do?
1) Provide such service.
2) Wear gloves, and if you drop something, don't pick it up.
3) Publicly donate proceeds from such events to organizations the group would find toxic. Repub party, gay to straight therapy, traditional marriage advocacy groups, etc.
If you do not enjoy poo-flinging contests, you will lose...ask yourself first, save the grief.
Now that's a brilliant idea! Advertise on your web site that 20% of all proceeds will be donated to an organization which helps gay people get straight.