@Alan McDougall,
To tell you the truth Alan, I'm not even really sure what it means to blaspheme the father or the son. Dictionary.com explains blaspheme as
-verb (used with object) 1.to speak impiously or irreverently of (God or sacred things).2.to speak evil of; slander; abuse.
-verb (used without object) 3.to speak irreverently of God or sacred things; utter impieties.
essentially bad mouthing God. I have doubts about how this pertains to the Holy Ghost though, because so few people have any real conception of what the Holy Ghost is. Biblical and Christian explanations of the Holy Ghost are vague at best. So it's kind of hard to legitimately bad mouth something that you don't even really conceptualize.
But I don't think that bad mouthing the Holy Ghost was what Christ was talking about anyway. I've heard a couple different claims about what it means to blaspheme the Holy Ghost, from anyone who speaks ill of the tradition of speaking in tongues, to anyone who simply turns their back on the church and leaves Christianity. These explanations leave me with the feeling that preachers promote it just to keep their followers in line.
I heard another explanation of it only once, but to tell you the truth, it was the one that seemed to make the most sense. As it is the role of the Holy Ghost to reveal the sons of Gods, (a role at least, I daresay the Holy Ghost aspect of God has more than one role,) that is to lead God's children into the kingdom, then as it was explained to me, it is blasphemy for anyone (and in particular church leaders are in a dangerous position to commit this,) to decide that any member of their body of believers is no longer welcome within their church. Essentially, by this explanation, it would be blasphemy for anyone to claim that someone else is not God's child, or to turn someone away from God's house, since only the Holy Ghost can proclaim such knowledge and has the right to deny entrance into Heaven. I don't know if this explanation is entirely right either, but of all the ones I have heard, it makes the most sense to me.