Answered by Shaykh Amjad Rasheed
Is it disliked for a Shafi`i to not recite the du’a qunut of fajr out loud sometimes, because most of his followers are hanafis and malikis so that they can see that he respects their school of thought?
As our Shaykh al-Khatib [of Tarim] said, the dislike of not reciting the qunut out loud is the evident position.
As for the followers, the basis is that this school is that of an acknowledged mujtahid Imam who was held in great esteem and one must take him into consideration in the same way that they want their madhhabs to be taken into consideration. So everyone must have adab (good manners) with the ijtihad* of the acknowledged scholars by not objecting to other madhhabs and their followers.
*Independent legal judgment based on the four sources of law