camel

Dear scholars, In Sahih Al-Bukhari we read:6417. Abu Qilaba al-Jarmi related that Anas said, "A group from 'Ukl came to the Prophet, may Allah bless him and grant him peace, and became Muslim. They disliked Madina and the Prophet, may Allah bless him and grant him peace, ordered them to go out to the zakat camels and drink their milk and urine. They did that and then regained their health. Then they apostatised and killed the herdsman and stole the camels. The Prophet sent [some people] in pursuit of them and they were brought and their hands and feet were cut off and their eyes gouged out and then they were not cauterised until they died."Firstly, what exactly did the Prophet ask the men to drink and why? Second, why does Islam punish apostasy, or does it not? I have heard that the majority of scholars say it is punishable but dont they understand that this is not right, especially uncer current circumstances. Is there anything that goes against this Hadith, and other general ones like "Whoever changes his religion, kill him" or "The blood of Muslim cannot be shed except in 3 cases: ......., he leaves Islam and joins the unbelievers" ?this is somewhat Fiqhi, so i thought it would suitable to send it here.