कल्पान्तरे विश्वासटिप्पन्यः

Source: TW

“śiśnadevā abrahmacaryāh” is from Yāska’s nirukta, substantially prior to Sāyaņācārya. It denotes those who are of unchaste/lascivious disposition, not the worshippers of the Śivalińga.

Why should Rgveda, which glorifies Indra’s sahasramușka-s, have a problem with the worship of something that bears Śiśna imagery?

Maithuna imagery is manifested in Śrauta rituals through suggestive/euphemistic words, ritual utensils, postures, to evoke union/productivity into being. There is no basis for claiming that the Veda had some special aversion to the Śiśna/phallus alone.

Of course, Śivalińga, while using phallic imagery, is much more than a phallus, as explained in a copious amount of tweets by myself. But this is a separate discussion.