You are talking without any substance for the sake of talking:
Your British Embassy in Pakistan is saying what the Americans are saying:
Information pack for British nationals arrested or detained in Pakistan - GOV.UK (www.gov.uk)
The Geneva Convention mainly applies to active land, air, and sea conflict zones. While there are laws on visas, it's laid out clearly concerning refugees, state-less people, and foreign workers and how things will be processed. However, nothing stops a nation-state from arresting you and dragging your *** to court. Also, nation-states can regulate their freedom of speech laws, and international regulations require local laws to be respected.
Now if you expect to be like that British National Shayan talk shit in London, and get a Visa to visit Pakistan and not have your as*-hole violated, then by all means, you try and let me know how the international conventions will protect you.
@jhungary wife is a lawyer and would be able to know more or explain more.