I'm not too convinced with this theory considering the following facts:
Babar Azam - he has not yet fully proved his potential, accumulating a meagre First-Class batting average of 27.06 from 27 innings. Even if his List A batting average is beared in mind (an average of 49.73 from 29 innings, with 3 centuries), I don't believe much damage has been caused to him and do not comprehend the fact that unrighteous attempts have been committed to ruin his career, especially considering he is merely 18 years old and has only started a career in domestic cricket.
Taufeeq Umar - considering the fact that Pakistan haven't played any Tests against any opposition since the South Africa - where Taufeeq Umar unfortunately became injured without playing a single Test - I adamantly believe not a single injustice has been afflicted upon him. Therefore, the theory that he has been discriminated against is totally ludicrous and disgraceful to even consider.
Aamer Sajjad - if one bears in mind that he doesn't exhibit confounding statistics in domestic cricket, it remains no wonder that he has not been given any opportunities at the international level. If players do not perform even at the domestic level, what can possibly make one think that they will perform at the international level? Again, your line of reasoning is baffling.
Adnan Rasool - considering he is not even from the city of Lahore, I for one do not acknowledge how regional bias can even be applied here. Even if he was from Lahore, despite the commendable domestic record he possesses, I can understand why he wasn't selected for the international team. The reason is simply that Pakistan have boasted a tremendous spin bowling attack in the last few years, meaning any fringe spin bowlers have been virtually unable to even show their credentials. For this, I cite the example of Zulfiqar Babar. Consistently performing in domestic cricket, he has only been able to make an international debut recently, and as is apparent, what a farcical mistake that has been by our national selectors - for he certainly could've been a greater spin bowler than Shahid Afridi and Abdur Rehman.
Junaid Zia - personally, I don't know how one can consider he was ever mistreated, considering he doesn't have tremendous figures.