Supporting a foreign team
Supporting a foreign team when the national side is playing against that team is a personal choice, of course. Anybody can do that on his/her sweet will. But such a choice proves his/her lack of loyalty to his/her country. And such a person is no better than Mir Jafar. This person deserves to be striped of his/her citizenship and must not be allowed to take any government job.
In a sport, when he/she can prefer another country to his/her own country, he/she can do it in some other spheres as well. The country must remain alert about such a person's activities.
This is a person who can get involved in espionage against his/her country for the benefit of any foreign country. The government may keep tabs on such persons. The next match in the Chittagong Zohur Ahmed Chowdhury Stadium is a perfect venue to detect such people. But this sort of people must not be physically punished.