Well if you're going to throw "backward" and "uncivilised" around to describe the nations we visited, isn't that being "anti" everyone else? The point is -- again, surely one that you should sympathise with -- that it ought to be these people's free choice to be "backward" and "uncivilised".
I wouldn't deny that British, etc, influence in Africa, India, etc has had benefits. Of course it has. The question is in weighing those benefits against the obvious disadvantages of going to another country, saying to its people "we're clearly more civilised than you are so we'll just have this land, thanks", and then generally treating the locals poorly for a long time. That is a very difficult calculation indeed; in part because really the only way to truly appreciate the effects colonisation has had you'd need to run a new history in which it never happened. Nor should we be held directly responsible for all the negative effects either. One unfortunate consequence was the spread of diseases, but (except for one or two incidents in North America, eg at Fort Pitt) this was unintentional and "just" rotten luck. Other consequences were certainly deliberate, malicious, and shameful. I don't think that bringing roads, railways, and universities to these places can make up for that.
Having said all that, what happened happened. I don't believe modern Britain should be obliged to say "sorry" for its past. Few or none alive today had anything to do with it. Instead, I'm for acknowledging the past openly. I think "pro-British" people often seem determined not to acknowledge that there were mistakes at all, or to try and divert the blame elsewhere.