Infant baptism is, same as adult baptism, founded in a promise to leave Egypt and journey towards the Promised Land, in this case made by the parents of the child who are vouchsafing before God that they will raise their child in the faith. Along these lines, "cultural" baptisms are a major abuse and it is incumbent upon the clergy to refuse to perform such.
Interesting. You are significantly closer to the credobaptist position than I would have expected!
I wouldn't deny the efficacy of a cultural baptism; I just consider it gravely unwise to permit.