Question

That's no reason to stop it.为什么不是There's no reason ...

如题，并请帮忙分析That's no reason to stop it.这种用法，谢谢

Answer 1

Teenagers like to gossip, and they often see something that isn't real. Perhaps your classmates cannot understand your friendship with this boy. That's no reason to stop it.
答：这句话摘自《 Unit_1_Friendship》的小课文。
That指代前面的这种情况，即同学们的不理解，不是你终止这种友谊的理由。
而there is no reason to stop it. 表示“没有理由终止这件事情”。意思不一样。

追问

那不应该是：
That's not the reason to stop it.吗？
即，我不是很理解that is no reason这种结构和用法，请帮忙分析下，谢谢！

追答

no=not a +可数名词单数
no= not any +可数名词复数/不可数名词

Answer 2

No reason 这里充当形容词作表语使用，意思可以理解为unnecessary 没必要。