What he is saying is that since the person who married that Pakistani Muslim is a Muslim from Kerela and as per Islam, a man is allowed to marry four.
However, here they must understand that in Islam you are allowed to marry up to four women provide you can do justice with all. Quran also say since you will not be able to do justice therefore marry only one.
Islam restricts 4 wives and gives guidlines, unlike other who do not restrict.
Since that gentleman was unable to do justice with the Pakistani woman, based on that as per Islam he was making a great sin and he shouldn't marry some one else.