It is reasonable to avoid upsetting recruiters - or at least avoid upsetting them too hard - simply because one never knows, one may need their help one day.
Accounting for above, still keep in mind that while you are employed (and especially if you are having a job you like), your position in this negotiation is really strong, much stronger than their.
talk to them on you own time and on your own terms. Since you currently have a job, you're probably not desperate, so don't cave in to bullying.
I may not tell them explicitly what is laid out crystal clear in above answer but this is definitely what I would have in mind when negotiating and in particular, when handling recruiter's calls.
From above, it is pretty simple to derive a "balanced" protocol. Since this is a two-way street (you're interested in new career opportunity after all), make a reasonable effort to accommodate.
It's OK that recruiters try to keep within their work hours. It's not OK if this is done "at your expense". As written above (and is worth repeating): do not forget that you are in stronger position.
- When called, first thing ask how much time they expect it to take.
If they can't tell, politely decline - most likely you're dealing with someone unprofessional. Remain polite since who knows, maybe few years later they will become mature professional and they might land you at the dream job. But now - just politely decline.
- If they tell you their expected duration, try to figure a time slot (yes, within your working hours) when it will be convenient to you to be out of office. If you can't figure it immediately, just ask them to call tomorrow to discuss the options.
Well, that's basically it. If they can't talk to you outside of your working hours, try to arrange for a time when it will be convenient for you to be out of office to talk.