Knowing how to present an argument persuasively does not change the argument of that student. Writers who do not sufficiently master writing for their audience will most often never be heard in the academic world. Academic writing is different from creative writing in that it must meet some quality requirements to be well regarded by others in that academic community. Beyond grammar and punctuation, students should be taught idea completion and development. The goal of education should be for students to take what they have learned and apply it to real world situations and sometimes this cannot be done with the type of writing that is taught in schools.
Education is for knowledge but it is also for practical applications of that knowledge.
There is no power is knowing something that cannot be used. Students would be better served by learning how to master techniques of writing and idea development instead of fearing it. Writing adequately is something that can be learned over time and with practice, just as any other skill and it should be taught this way. Education is lost in the minds of students if it can not be expressed and shared with others in academia.