Well I can see both sides.
I would be nervous about taking my dog as I know he doesn't have reliable recall when distracted and though well socialised is far too keen to meet other dogs.
I have no doubt he would want to charge up to greet Rex (or any dog) if he was offlead, I also have no doubt if told off (by the other dog) he would submit immediately but do I have a right to allow my dog to cause stress to another dog ??
I don't think so.
I don't think we would gain anything training wise or fun by keeping him onlead in case another dog took a dislike to him and a fight started
I don't have any fenced offlead areas around here to 'practice' in, I take him to my park on a flexi lead and occasionally let him off for a bit of a run once he is more worn out and only if it is really quiet and my confidence is high, I'm too scared he will go on the road and get hurt
Myszka has seen my Jones bolt for a poor lady at the park and he was totally DEAF to me !!! He was only being friendly but it is scary for the other party and in my view unacceptable and I take full responsibilty for his bad behaviour !!
*yes I changed my ID again Myszka :p Hope you had a lovely holiday and are well.