Why someone is religious is irrelevant. If you are, it means you believe in G-d, and therefore you CANNOT accept that for others its ok not to be religious. If you believe “a religious life is not for everyone”, then you’re not religious.
This has nothing to do with proof – its simply not helpful to tell a religious person to view it as ok if their child does not want to be religious.
This also does not mean you cannot still show unconditional love for your child. But yes – you are religious, so you do not accept their choice.