I Don't mind is used a lot in different contexts , It can be meant as not taking offence at what someone said
EG ... " Please don't be offended but your ass looks fat in that dress .." Reply " I dont mind at all " THWACK ...
But as in this case " I dont mind " means that I don't have an opinion either way and will go with the majority rule ...
It can also be used , if you borrow something, " Can i borrow your mirror? " " I dont mind" = yes if you want,
Hope that clarifies it ... there's probably lots more examples
"I don't mind" , is a polite way of saying " I don't care" which would be considered rude.