I think that is very cheeky.
Whilst hamsterdog has some reactivity issues when she is on lead and another dog charges her , and we have yellow ribbon/bandanna as she reacts if the lead gets tangled as she feels she can't escape, I think they were YABU if they were going to keep theirs off lead- YANBU if they were about to leash theirs and yours were charging and acting up, but not if they weren't within their general walking space.
That said I do ALWAYS shout across to other owners when I let ddog offlead first to check theirs are friendly. If not I either wait til they are gone, or go to the other side of the field to let ddog off (ddog is good 98% of the time but has kevin episodes occasionally despite having an almost rock solid recall ).
The only exception is if the dog was of someone that ddog had played with before and even then I would wait for a wave/thumbs up unless you are particularly close to the owner.
Generally this is what I try to do- sorry if I'm getting this wrong but I want to help others to the best of my ability.:
Yellow ribbon/bandanna: Give wide berth, do not approach dog or owner, try not to let yours bother theirs within a 5m vicinity. Don't let yours charge theirs under any circumstances.
"In training" jacket- Give wide berth and yell for permission
On lead: Approach and ask permission, but only if they are walking torwards you, some may be trying to train their dogs and head off in the opposite direction. Dont let yours charge, but a polite approach off lead not under 5m is generally accepted. If yours charge, apologize and get yours back on lead/under control, we have probably all been there at one point as dogs or humans are not 100% perfect, just dont scarper leaving your dog to barge my dog on a lead to the other side of the field 100m away.
Off lead, under very close control: Yell and ask permission, keep yours under very close control or put on lead, theirs might be ok as long as not interrupted and greeting is controlled when both parties agree.
Off lead, under close control: Yell and ask if friendly with other dogs
Off lead, under control but of significant distance and playing with other dogs, normally "fair game".