From Buddhas point of view, is what is common called preaching unskillful not benefical?
"Preaching" in the sense of "proselytizing" is kind of unpopular among Buddhists (see also How are Buddhists supposed to spread Buddhism?).
In the suttas I think that the Buddha tended to teach people who asked him a question or people who challenged him (and didn't try to impose his views on strangers), and he often taught by asking questions.

But "preaching" in the sense of "giving dhamma talks" is normal; and (Dhamma) is I think defined as one of the proper topics of speech for a monk.