Pubs having a policy of not serving people in uniform is not new and regrettably occurs in many places. Servicemen have a reputation of creating or being the cause of disturbances in some places. I gather that on this occasion their commanding officer was at the funeral and it would be interesting if he too was refused entry.
"I cannot understand why a bar would have a policy of not serving people in uniform."
I can. They've obviously had trouble with soldiers in the past.
This incident shouldn't have happened, but I'm guessing that the owner/manager wasn't present at the time, and the duty staff blindly operated the policy without stopping to think.
It shouldn't have happened, but it did, and I imagine that everyone involved regrets it. Mounting campaigns to boycott the bar involved is a ridiculous response to a single unfortunate incident, but I guess there are plenty of people only too ready to jump on the bandwagon.