Yes, I agree that if a primer is leaking in the cockpit, that is unsafe, and should not be flown. There are several possible causes for a leaking primer, all of which are maintenance issues, and beyond the scope of the pilot.
Letting alone the obvious fire risk of fuel in the cockpit for a leaking primer. If it is leaving out fuel sometimes, it is probably leaking in air at other times, and this could have a small affect on the operation of the engine, depending upon where the primer nozzle is in the induction system.
The aircraft in that condition is not airworthy, and should not be flown. Suggesting mitigations as to flying it in that condition is not a great idea. If you're stuck in the bush, and have to get the plane out to save a life, perhaps, but to just go 'round the patch for an hour, that plane should not be flown until repaired.