The first fallacy in this argument is that in a decriminalized environment "drug dealers" would be a threat to public safety. Or are you actually claiming that liquor stores and pharmacies are a "threat to public safety"?
The drug dealers we get via the current Prohibition certainly are, though. Way to go, keeping them in business.
The second fallacy is that libertarianism doesn't allow threats to be dealt with.
Crack equals beer? Smack equals aspirin?
Libertarianism's foundation.