Fr. Girzone (The Joshua novels) warned me away from the Catholic Answers forum. They had excommunicated me forever because I unwittingly offended one of their members by debating purgatory. (At least I think this was it. They never told me what I had done to so seriously offend the faith of Catholics).  
    Searching online I found many sites hosted by those with a mortal in mentality about Sunday worship. Then there are the two Catholics I know locally, one from a parish in the next town I am familiar with and another with whom I attend a seminar on classics in religion at a local library. (I presented on Thomas Merton recently.) Both in discussion believe it is a mortal sin to miss Mass on Sunday. 
    Then there is a book on Catholicism where the author writes that he thinks this idea is the greatest mistake the church ever made. (I can think of worse.) 
     It is an issue that can keep the intellect challenged. Boredom and mediocrity are worse. Thanks for your reply.