Like the ignoramus, the bullying traveller, has an over-inflated sense of entitlement and enjoys a fleeting sense of personal empowerment, by belittling a fellow traveller or person in a service position.
Often they come from professions that gives them considerable authority or a degree of expertise, where they become used to giving orders as part of their modus operandi.
One bully on a tour can ruin the dynamic of the entire group.
Bullies believe their own opinion is more valuable and far more superior than any one elses. They will cut off the contributions of other group members in a way that lessens their import.
The bullying traveller often attempts to divide a group, by creating a heirarchy of those they deem worthy or unworthyy to associate with. They thrive on gossip and use both covert and overt means to set up a target to marginalise and make miserable through their nasty domineering tactics.
Bullies on tours should be challenged.
The problem is that bullies thrive and rule by establishing fear. Speaking up or asserting yourself against them if you are targetted by them is not easy.
I believe bullies must be amongst the most insecure individuals on the planet. Why else would they inappropriately and deliberately abuse power in a context and amongst people they have never met before, nor are likely to encounter again?