that it was merely disliked, and that—so they argue—dislike does not contradict permissibility when it is only a matter of tanzīh (non-binding discouragement)!

Ibn al-Qayyim states in Iʿlām al-Muwaqqiʿīn (1/47–48):

“Al-Shāfiʿī explicitly ruled that it is disliked for a man to marry his daughter who was conceived through fornication, and he never once said that it is lawful or permissible. What befits his dignity, his imamate, and the rank Allah granted him in the religion is that this expression of ‘dislike’ is meant as outright prohibition; he simply used the term ‘dislike’ because whatever is unlawful is detested by Allah and His Messenger. The Exalted One, after listing the things He has forbidden—beginning with His words, ‘Your Lord has decreed that you worship none but Him…’ ⦗1⦘, then ‘and do not kill the soul which Allah has made sacred, except by right…’ ⦗2⦘, then ‘and do not pursue that of which you have no knowledge…’ ⦗3⦘, and so on—concludes by saying, ‘All of that, its evil, is detested by your Lord.’ ⦗4⦘.”