That's a load of rubbish, anyone can use any level of force up to and including lethal to protect themselves or others, as long as it's "reasonable" under the circumstances.
This is exactly the same position as the police are in, with the exception that the police are legally allowed to carry what would normally be classed as offensive weapons to assist as it is recognised that they are expected to face situations where they'll need them to perform their duties on a regular basis.
The only people that others are calling racists are those who lump every muslim in with the terrorists, a lot of the people treating those injured will be Muslim, in other attacks it's been Muslims who have been involved in trying to stop the attackers or running in to help the injured whilst the risk is still high.