Answer

Simply speaking, according to the law, glass vessels do not require kashering at all (certainly if they were not used for hot food). Even the Rema, who is stringent regarding glass, the commentaries on his ruling wrote that this is apparently only a stringency for Passover (for regarding wine handled for idolatrous purposes, in Yoreh De’ah, he did not disagree with the Shulchan Arukh, who said that glass does not absorb). If this is merely an extra stringency, then there is no need to be stringent, and one may eat in accordance with the local custom. But if in your view this is an actual prohibition, then there is no permission whatsoever to follow the custom of someone who disagrees with you.