Its the Karachi Kings lobby that has become active against Muhammad Rizwan. Shaibi is connected with it through Rashid Latif and Wasim Akram. It did not look good on them that the player they sidelined and ditched, was picked as captain by Multan Sultans and is performing so well in t20s.
Ever since the selection of Sharjeel Khan for South Africa tour, Shoaib Akhtar and company (Dr Nauman Niaz and Rashid Latif) have become irritated by the fact that Muhammad Rizwan has consolidated his position in t20s as opener and their favorite Sharjeel Khan was largely ignored by the team management. Before that they were not that rude about Muhammad Rizwan because Sharjeel was not in the picture and they were hoping that once Sharjeel returns, Muhammad Rizwan will get automatically demoted to lower middle order. But Muhammad Rizwan performance as opener is top notch and Shoaib Akhtar and co are getting frustrated that Rizwan is performing so well. Even before the tour to SA and Zimbabwe, Akhtar and co used to criticize Muhammad Rizwan's performance as opener (pointing out low strike rate in the first six overs) and insisted that Sharjeel is the ultimate solution. 
I recall that in game on hai show during t20s against Zimbabwe, Shoiab Akhtar blurted out same rudeness against Muhammad Rizwan that he should adjust down the order otherwise doors of exit are open for him, and that "kisi kay baap ki team nahi hay". The host kinda looked surprised (as Rizwan had given match winning performance in that match) and shared the opinions of people that Rizwan wont be so useful in lower middle order as he needs some time to adjust and he will get few balls to do power hitting. Shaibi then said :" then he should rotate strike". 
Besides Rashid Latif, I think Shaibi is also getting influenced by Wasim Akram who is dismissive of Muhammad Rizwan (as evident by some of his statements). Imo Wasim Akram was the one, not Imad Wasim, who sidelined Rizwan in Karachi Kings. Wasim Akram would also want Sharjeel's inclusion in the national team on regular basis as it will look good on his KK franchise. Rashid Latif is also supporter of Karachi Kings. This is the lobby that wants to sideline Muhammad Rizwan.