Lecturers do not usually tell students they’re plain ‘wrong’ unless they really are barking up the wrong tree, in which case they need to be told so that they can get back on track.
Lecturers are not divine so cannot claim to be infallible but they are generally better informed than their students. They are also the ones setting and examining assessments 🙂
When you finish your degree you will know that your academic skills and subject knowledge have developed considerably since your first weeks at university. This is even more true of someone who has researched at post-graduate level and taught for many years.
If you want to ignore your lecturer’s expertise then you are free to do so but you’re going to be missing out and making life more difficult for yourself. Student life is hard enough – make the most of any expertise and help on offer!