NO! Never pitch out a batch until you absolutely know for sure it's infected. You have a great chance of it being fine! It happens all the time. Search for blow off tube and you'll see what I mean!
Just clean the airlock and the lid, resanitize and stick it back on. So much co2 is coming out, it's highly unlikely than any bacteria or wild yeast could come into your beer. Don't worry about it. It'll be fine.
Broken Leg Brewery
Giving beer a leg to stand on since 2006