Security is about trade offs. Talking about absolutes makes barely sense in this context, because any perfectly secure system is also perfectly useless.

Despite the chosen solution on SO - and from how the question is stated, it is clear that the asker only wanted confirmation -, sudo has its uses, even if is not perfectly secure (especially with the default configuration).

I suggest a more sensible approach for all security-related discussions: All systems have vulnerabilities, but some improve your security posture.