If you read your own link, it says benefits for the families of terrorists - there is a difference.
If someone goes to prison for drink driving, should his wife and children be denied benefits? They are innocent.
If someone goes to prison for fraud, should his wife and children be denied any benefit? They are innocent.
Likewise if a man is convicted of a terrorist charge, the wife and children have done nothing, they are innocent, and should be treated the same as everyone else.