There's honesty when you're asked an opinion, and there's also social conventions, laws, and normal behaviours that ensure things keep functioning smoothly.
If someone asks me an opinion, I'll happily give it. I will always be honest, because that way it ensures that in life people who like 'you for you' gravitate towards you and people that don't particularly like/agree with your style personaltiy generally still clear. People can smell a lie, awkwardness or dishonesty a mile off and it makes them uneasy. It's always best to be honest in a social situation. And personally I like that honesty from Harry. If he says Bongani couldn't get a game from Reading, well it's true. Saying 'I only have Bongani, who is an excellent option to have but I've actually never taken the opportunity to play him for some unknown reason' it would clearly be gonads. It wouldn't motivate Bongani to hear he is on the same level as King and Gallas. He isn't as good as them and being told that he is won't make it so. Honesty is the best policy when motivating people too, and hearing that he the manager doesn't rate him on the same level as his other centre backs may make him step his game up. It may not, but in won't make it worse because he wasn't going to get a chance anyway unless he became good enough. Wenger has admitted today that Arsenal were over-reliant on RVP. Some people on here that don't like hearing the truth may have sympathy for the Arsenal players (maybe if they were Arsenal fans in this example) because it means that guys like Song, Walcott, Koscielny have been put down. But in actual fact it won't make them play worse to hear that, because they know it's true. All it might do is make them step up to have more of an impact themselves.
But when it comes to social conventions, people don't go around telling everyone else they are a **** because a lot of the time, it isn't true. If they were really being honest with themselves, they'd understand that they don't really know that person, and if they did, there's probably plenty of people that think the same about themselves, and so nothing needs to be said. Also, if they were being honest with themselves, they probably wouldn't want a smack/to get arrested/to have people dislike them. So it is left alone.
In the case of Harry, he's only said the truth. He hasn't articulated himself well, but that's because he isn't the most articulate person. But what he has said isn't untrue and it isn't offensive. Some people just can't handle the truth.