if a parent feels that their child is old enough and mature enough to get married, wouldnt it follow that their child is old enough and mature enough to pick a suitable spouse? i can understand that there may be objections which come up over time which may not have been present or known about at the time that the shidduch first came about.
there is nothing wrong with discussing opposition or anything else, but ultimately the choice should be up to the person getting married. there are times when intervention is needed, but that is NOT the majority of the time.