Short answer is, Scripture says all those that believe on the word of God were baptized. If a man believes on Christ and understands the difference between good and evil then to be saved he must be baptized. If his parents do not accept it then it would be a case of obeying God rather than man. No matter the punishment he will receive in this world he should be baptized if he believes on Christ. If he is punished he should rejoice just as every true christian has since the time of the Lord's death and resurrection on wards.
Long answer is this:
We are saved by Faith alone(Ephesians 2:8-9) but we are justified by faith and works(James 2:14-26). So if we have faith we will keep the commandments of the Lord(Revelation 14:12-13; John 14:15-21). One of Those commandments, and one of those works that must be done, is that we must be born again(John 3:1-8; 1 Peter 1:23; Colossians 3:10; 2 Corinthians 5:15-17; Titus 3:5; John 1:11-13). Baptism is the means by which we are born again(Romans 6:3-11; John 3:2-7; Galatians 2:19-20; Colossians 2:10-15,19-23) born in the spirit(John 3:6; Galatians 4:29). In order for the Baptism to work you have to have a name(Matthew 28:19-20; Acts 2:38; Acts 19:5). Not just any name but a name so special, powerful, and unique that it was the only name of its kind given under heaven(Acts 4:10-12; Matt 28:18-20; Acts 10:48). A name given to us by God Himself, given to us in God's own name(John 5:43)(Yah). The bible speaks in great detail on this matter, and does not fail in stressing the magnitude and importance of the only name heaven has given us to be saved.
1. In order to saved you must first believe on Yahshua the Christ
John 3:3
John 3:15-18
John 3:35-36
Acts 16:31-33
John 6:47
John 5:24
John 14:1
Romans 10:8-9
Hebrews 11:6
Acts 10:43
1 John 5:4-13
Mark 16:16
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2. We must believe that Christ was God manifest in the Flesh
1 Timothy 3:16
Colossians 2:8-9
John 1:1,14
John 8:28
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3. Must believe Christ lived a sinless life
1 Peter 2:22
2 Corinthians 5:21
Hebrews 4:15
1 John 3:5
1 Peter 1:18-19
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4. Must believe Christ died for all mans sins
Luke 1:77
Acts 13:38
Hebrews 10:16-18
Luke 24:45-47
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5. We must believe he raised himself from the Grave on the Third day
John 2:19-21
John 10:17-18
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6. We must repent of all our past sins and ask the Lord for forgiveness in the name of Yahshua the Christ
Luke 24:45-47
Acts 2:36-39
Luke 3:2-4
Acts 3:18-21
Matt 4:17
Revelation 3:19
Acts 17:30
Luke 15:7,10
Mark 1:4,15
Luke 5:32
Matt 9:13
Acts 8:16,19
Acts 10:43, 48
Acts 19:5
Acts 22:16
1 Cor 1:13
1 John 1:8-10
Acts 13:24
1 Cor 12:13
13 For by one Spirit are we all baptized into one body, whether we be Jews or Gentiles, whether we be bond or free; and have been all made to drink into one Spirit.
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7. We must forgive all those who have sinned against us or we will not be forgiven
Matthew 6:14-6:15
Matthew 18:15,21-22
Colossians 3:12-13
2 Corinthians 2:7-11
Ephesians 4:32
Mark 11:25-26
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8. One name given under heaven given unto man by which they may be saved, Yahshua the Christ
Acts 4:10-12
Matt 28:18-20
Acts 10:48
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9. Baptized into Christ's death and born again into everlasting life
Romans 6:3-11
John 3:2-7
Galatians 2:19-20
Colossians 2:10-15,19-23
1 John 5:5-8
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10. Must be Baptized in the Name of Yahshua the Christ Alone for forgiveness and remission of Sins
Matthew 28:19-20
Acts 2:38
Acts 19:5
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11. Every single person that believed on Christ was baptized
Galatians 3:26-27
Matthew 28:19-20
Acts 2:38, 41
Mark 16:16
1 Peter 3:21
Acts 22:16
John 3:5
1 Corinthians 12:13
Acts 19:4
Acts 10:48
Mark 1:4
Acts 8:36-38
Acts 16:31-33
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12. Baptism is a requirement for salvation, every person who believed on Christ was baptized. All those who believe and have the ability to be baptized need to baptized in order to be saved. Unless you are born again of water and spirit by the Blood of Christ you cannot enter into the kingdom of Heaven.
John 3:1-8
1 Peter 1:23
Colossians 3:10
2 Corinthians 5:15-17
Titus 3:5
John 1:11-13
1 John 5:5-8
That is what I would tell your friend. So long as he Truly believes these few things, is Baptized by full submersion, in the right name, by a man who believes the same, then he will be just in the eyes of the Lord Regardless of the punishment issued by his parents.