The problem with this argument isn't that natural language programming leads to vague/ambiguous code that would lead to errors. The problem is that the machine does not inform you of the ambiguity. Rational humans do just fine when they interact because they can identify these problems. Programming would work just find if context were identify and clarified while the code was being written.
If I were to tell a program to "buy political ads in Portland," yea, the point is that the program would need to know which Portland I mean. Otherwise it might accidentally think I mean Portland, OR, instead of Portland, ME:
https://www.yahoo.com/news/politics/articles/25-000-mistake-...
Humans can do the same thing if they're not being careful. The point is, the vast, vast, vast majority of time, someone would just say "wait, you mean Portland, Maine, right?" and you'd say "yes" and that would be that.