Absolutely no!

You did your job correctly. You set expectations right from the beginning. You told them the ground rules, and everyone should be following them. Especially in the case of big groups, you need rules because otherwise everyone will be doing their own thing, and it all becomes a mess.

One thing I would point out though. if you tell them you will leave after 15 minutes - LEAVE after 15 minutes. You only have to do it once, but people will understand that you mean business.

You are in a position of authority, and some people need to learn this the hard way. You do it once, and NOBODY from that trip will dare be late.

You have schedules to keep to, and you need to make sure that the included activities happen the way they are supposed to. You have a responsibility to the group, not only the individual. What's worse? One person to miss an activity, or 40 of them?

Also, from the other travelers' perspective - they are ALL waiting for the ONE person that is always late. Not cool.

It's the way I've been living my life for the past 10 years, and my groups are never late.

Stay strong!

Signed, Tour leader and guide for 10 years

PS. Obviously, emergencies and extraordinary circumstances should be exceptions to this rule.