Destroying a cultivation family is something that the disciples of the Blood Skull sect are more than capable of doing, but should not do because the sects have a pact with the Blood Skull sect not to do something like this.
The other four sects gave the Blood Skull sect a lot of benefits in exchange for the Blood Skull sect not going around killing people without reason. So it is a pact of peace.
The key word here is reason. The Blood Skull can still attack and wipe out large forces as long as they are justified. So anyone in the Blood Skull sect is looking for any excuse desperately.
Because of this, Arthur won't need to beg anyone to help him destroy Argo and his family. Once he gives the disciples of the Blood Skull sect an excuse, they will thank him and even owe him a favor.
