لَا يَزَالُ states ongoing existence. In لَا يَضُرُّهُمْ, the pronoun هُمْ refers back to the steadfast group. حَتَّى يَأْتِيَ أَمْرُ اللَّهِ marks an endpoint.
Together, the clauses say that faithful people will remain and opposition will not make them abandon their essential course. This does not by itself identify any particular contemporary organization as the sole group meant.
The ethical response is principled commitment supported by knowledge and good conduct.