All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
Any kind of cooperation with evil is forbidden, Allaah Says (which means): {And cooperate in righteousness and piety, but do not cooperate in sin and aggression. And fear Allaah; indeed, Allaah is severe in penalty.}[Quran 5:2]
Intoxicants and the one who helps in drinking it were cursed by the Prophet who said: "Allaah has cursed intoxicants, its drinker, its server, its seller, its buyer, its presser, the one who demands it to be pressed, its carrier, the one to whom it is conveyed and the one who consumes its price." [Abu Daawood]
Based on the above texts, the prohibition applies to cooperating in any other evil. If the reality is as you mentioned that Muslims cooperate in selling liquor and pork then their earnings are unlawful. They have to repent from this sin and should give up such jobs. Indeed, whoever gives something up for the sake of Allaah, it will be replaced with something better for him/her. Allaah Says (which means): {And whoever fears Allaah—He will make for him a way out. And will provide for him from where he does not expect.}[Quran 65:2-3]
In fact, the above mentioned problem is one of the reasons that make living in non-Muslim countries unlawful. Because, earning lawful livelihood in those countries is very difficult if it is not impossible. The Prophet spoke truth when he said: "I am free from any Muslim who resides among the polytheists [non-Muslims]." [Abu Daawood]
To know the ruling of living in a non-Muslim country read our Fatwa: 81642.
A Muslim should be an example in his good qualities. If he implements the teachings of his religion, most probably, he may inspire others to embrace Islam. If his actions are contrary to what be believes to be prohibited he may deter people from the religion of Allaah, the Most High.
Therefore, a Muslim has to aspire to earn only what is lawful because it brings the blessings of Allaah and causes supplications to be answered. So, you have to keep yourself away from unlawful earnings since they eradicate the blessings and hinder supplications from being answered.
Allaah Knows best.