The advice is being given as it signals that the person isn't interested in a non-professional relationship. It would probably be more direct to just say "I hav

The advice is being given as it signals that the person isn't interested in a non-professional relationship. It would probably be more direct to just say "I have no interest in a non-professional relationship" but, I assume, people who are comfortable with that level of directness probably wouldn't make use of the advice. The advice will have no help in a genuine harassment situation as the harasser isn't going to give a crap but the assumption is that misunderstandings are more prevalent than actual harassment. If that's not the case then, yes, it's bad advice as it won't work. It has nothing to with respect or lack of it. It's intended as a signal. If someone has so little self respect that they can't say this without feeling diminished then, yes again, it's bad advice. However, I have a feeling that the original author of the advice was aiming it at the many young, smart, confident women who attend tech meet ups and want to avoid awkward situations. As such it strikes me as sensible, practical advice for said audience. But sure, maybe not for everyone in every situation.