“No one can be received into the church of Christ unless he has arrived unto the years of accountability before God, and is capable of repentance” (D&C 20:71)

This is plain and simple to understand. Membership in the church should commence when an individual is confirmed after baptism and is accountable.
This scripture is very specific when it states “No One” is to be received as a member unless they are accountable which in the case of children we know to be eight years of age (D&C 68:25). Little children are pure before God and have no need of repentance, baptism, or confirmation (membership) into the church. (D&C 29:46-47)
The ordinance of the blessing of children (D&C 20:70) has nothing to do with actually becoming a member of the church. I understand we call them ‘children of record’. What record? Is not this the membership record? Those who are not blessed are not counted as members.
In my opinion counting children under the age of eight as members is precisely against what the Lord is declaring in the above scripture when he states “No one can be received into the Church of Christ”. All that we endeavour to do should be in accordance with the revealed word of God.
Surely we do need to keep a record of our children with their parents on the membership records but like children over the age of eight and unbaptised they should not be counted as members of the church as is the current practice.

JOEL - Here is the scripture in question:

"No one can be received into the church of Christ unless he has arrived unto the years of accountability before God, and is capable of repentance.
Baptism is to be administered in the following manner unto all those who repent."(D&C 20:71-72)

In my opinion I think you are being a little to strict and literal on your interpretation. To me the main point of verse 20 is not so much about church membership, but that children do not need baptism because they do not need repentence. But for the sake of argument let's say it does mean membership. If those children under 8 should not be statistically considered members of the church, then what church should we say they belong to? If an LDS seven year-old's non-member friend asks him what church he belongs to, what should he tell him?
As you say, according to the D&C, as far as God is concerned, they do not yet need to be "received into the Church of Christ"(D&C 20:70), because as children they are already members of His kingdom of heaven (D&C 29:46-47). Being "received" into the church is not the same thing as being called a "child of record", even though both conditions could be seen as declaring a membership. Being "received" into the church requires baptism, confirmation, and announcing the performance of the ordinance to the general membership of the church.
Even though they are not yet baptized, in the eyes of the world they would be considered members of the church when blessed as infants, because the blessing implys that the parents intend to raise the child in the LDS church. Those little 1 to 7 year-old bodies do occupy space in our churches every Sunday(sometimes more than they should). To me we are talking about two types of members; baptized members and not yet baptized members.
Counting them as members provides for a more fair and equalized statistical comparison between the LDS church and churches that baptize infants such as the Catholic, Lutheran, Episcopalian, Presbyterian, and Methodist churches. Whenever the church announces their statistics they do specify how many of the total members are "Increase in children of record", just in case someone wants to subtract that number to get the "real" membership number. So it's not like were trying to hide something.