Hymie, there's a subtlety here. Truth "justfication" is a defence to a libel action, any libel action.
There is another defence which used to be called "fair comment", now "honest comment". That was the defence which was, and is, available to book and theatre reviewers. They are entitled to give an opinion on any work, such as a play, put before the public and it does not matter if that opinion suggests or states that a performer or writer is bad or incompetent in it, so long as the opinion is genuinely held. This defence is now also available to scientists and other specialists. In one case a scientist said, in effect, that a treatment and medicines offered by a company were mere quackery, and didn't work. The company sued. The court held that provided that the opinion was based on some facts which were true AND it was in the public interest that the opinion be published then the defence of honest opinion was open to the defendant. You see, it does not matter that there may be other facts which could be taken as showing the opposite; a scientist is entitled to draw on his expertise to form a judgment on the evidence and give that opinion.
There is another circumstance in which the truth may be libellous. It may be possible to assemble a series of facts, all true, and put them together to make a libellous whole That is innuendo. The clear message, the suggestion, in the piece may be taken to be one thing yet none of the individual facts is untrue. For example, that a married man is booked into the same hotel, is seen in the company of, is seen leaving the house at 4 am, of the same single woman together with a few other careful details (his wife was away etc) can be presented as a clear suggestion that he's committing adultery, yet it is never stated in terms