I am sorry.. but I missed where the gentleman actually answered the question?
In his opening statement Zakir Naik says that if you say in the context that we as human beings are all the children of God, I can accept that assertion. He then added that if the context is of obeying God than all the Prophets and Messengers of God are children of God.
From 1: 27 onwards he explains the problem is when someone says that Jesus is not a normal son, but a begotten son then that is where the distinction is made. He adds that in biblical language God has 'sons by the tons' [pardon the expression]
He then cites examples of such 'sons' of God in the Bible [not accepted by Islam, but accepted by Christianity and with some variations by Judaism]. They include-
Adam [the first human being]
Ephraim
Israel [Also known as Jacob, the father of Joseph and the twelve tribe of Israel, hence his title 'Israel']
He then explained that in Romans Ch 8 it says that 'all those who are led by the spirit of God, they are the children of God'
He says that the biblical expression means that if you follow the Commandments of God you are a son of God.
Now if I can digress slightly.
'Spirit', if I can add in the Bible has many meanings and depending on context, it can be interpreted in so many ways. One of the meanings of the word 'spirit' in the Bible is 'Prophet', 'Messenger' and 'Apostle of God', hence here the context is of someone sent by God therefore whether the 'spirit' is an angel, a human being or otherwise it still refers to an emissary sent by God. As the expression holds, if a 'spirit' is to be followed, it will be a human being and not an angel as angels are sent to Prophets, to specific individuals and not to the entire human race and are not meant to lead humans but to help in any lesser way or manner.
Returning to the topic, at 1:48 he then added 'today that phrase ('son of God' ) has been misunderstood'.
He asserts that if someone says as an elder to a younger person, 'son, its a very good question' he [the younger man or boy] won't mind. But, if the same elder was to say 'begotten son' in the same context, the same younger man is likely to get angry and perhaps resort to violence as the context is no longer of respect but of the question of progeny between them and one the latter is likely to dispute and be inflamed by.
The Christian, Zakir Naik says, argue that Jesus is not being addressed in the first sense, that of a child of God based on being a human being alone or a good and righteous follower and loyal servant to the Commands of God. The Christian instead says that Jesus is a son of God in a different sense; that of being a begotten son of God and the evidence cited by the religion of Christianity is the Gospel of John Ch 3: 16 where it says 'God so loved the world that He gave his only begotten son [Jesus]... whoever believes in him [Jesus] shall not die but have everlasting life'.
Zakir Naik then said that this is from the KJV [King James Version] of the Bible. The Revised Version [published centuries later by Christian scholars] add that the word 'begotten' is a fabrication and an interpolation inserted into the Bible and is not found in the original manuscripts of the Bible. The Revised Version therefore expunged the word 'Begotten' from the Bible.
From 3: 47 Zakir Naik then focusses on the word 'begotten' as a word itself. He describes it as a sexual and lower animal act and then says 'when you say that he [Jesus] was born to mother Mary, virgin what are you insinuating'.
He then adds the Qur'an disagrees, it instead says in Ch 3: 59-
'The similitude of Jesus before Allah [God] is the same as Adam [the first human being]. He [God] created him [Adam] from dust, then [He i.e. God] said to him: 'Be! -and he was'.
Zakir Naik then asserts that if the Christian argues that Jesus is the son of God because he has no father then Adam in the same line of argument is a greater and more significant god, because he had neither a mother or a father according to the Bible.
Later on from 5: 30 he explains the Qur'an omits the attribute, 'father', as a description or title of and for God. This is because in subsequent centuries in the sending of prophets the term lost its original figurative and actual meaning among the people and became known wrongly with the literal meaning alone. He added the word 'Messenger of God' is what is meant by 'son of God' in which case all the Prophets being His most loyal followers are 'sons of God'.
My personal inference to this [and not the words of Zakir Naik] is that by default in the same manner, 'father' in the spiritual sense is a reference to God as lawgiver, guide and patriarch and not 'father' in the literal sense.
From 6: 20 until the end Zakir Naik addresses different topics within the same framework; that being following the commands of Jesus, following the commands of the original law as given to Moses [hence the name Mosaic law] that Jesus himself followed.