It can alienate audiences without good reason. About half of all people are female. The use of Man, he, him, and so forth to refer to people is alienating, archaic, and imprecise. The presentation will not be convincing if the speaker does not exhibit conviction. State the case clearly and offer the strongest support for it.
People can then choose to agree or disagree on the merits.
Finishing early leaves more time for questions, and shows appreciation and respect for the time the audience members have taken to attend. A good presentation is hard work. Spend time researching, writing, and honing the presentation. People who fly from place to place giving presentations or who give presentations often should continually replenish fluids. Water is best, juice is next best.