Is it right to sue for defamation of character if a journalist reports false information about a person?

[adusa37]

A journalist named 'A' received a report about a rumor that the government employee 'B' took ten thousand dollar from a construction company and gave them the building permit.

'A' interviewed the workers of the company and they said 'it was difficult to get the building permit, so 'B' must have received money'. When he asked 'B' about this, he answered 'there must be a problem in giving the permit, but I haven't received money'.

'A' tried to ask the owner of the company, but he was on a business trip abroad. Thinking it is obvious that the owner won't tell he had given money even if he had, he didn't interview the owner.

He made a decision that it's true that there is a problem in the building permit and there is high probabilityof 'B' receiving the money and wrote an article that 'B' is suspected to receive ten thousand dollars from a construction company and gave them the building permit and it appeared in the press.

Later, it came out that the article is incorrect and B didn't receive money from the company. And 'B' sued 'A' for defamation of charactrer.

Do you think 'A' should be punished? (It would be better if you gave specific reasons)