Typical 'hardshell' who walks on the fringes and if he is typical of many, lacks the fruit of the Spirit of which they ignore and neglect but in self-examination should be of great concern personally. I would also guess he is taking WCF XXVIII:v out of context which reads:
V. Although it is a great sin to contemn or neglect this ordinance, yet grace and salvation are not so inseparably annexed unto it, as that no person can be regenerated, or saved, without it: or, that all that are baptized are undoubtedly regenerated.
This article is addressing baptism in general and not infant baptism in particular. If you read the entire chapter, you will see that confessional Presbyterians do not believe that sign and seal of baptism does not automatically belong to everyone who is baptized, including infants. Article VI that follows makes that very clear, where it states in regard to the efficacy of baptism, "to such (whether of age or infants) as that grace belongs unto
, according to the counsel of God's own will, in His appointed time." In other words, the sign and seal [efficacy] are infallibly bestowed upon the elect
and not necessarily at the moment of baptism. Children are NOT an exception to this but included,
I have been 'rebuked' by men far better than him, so that if he should have the occasion to do so, I would undoubtedly smile.
This conversation, if one could call it that, which you are having with this person is one of those which you are enjoined by Scripture to shake the dust off your Nikes and move on.