A friend of mine has been issued with a verbal warning because of his "attitude"... i.e. the boss received complaints from other employees about my friend's attitude. When he (my friend) asked for examples, none could be supplied and it was put down to "many small" issues, that amounts to an overall bad vibe. The boss did say that he has no issues w.r.t. this employees work or standard of work, but feels that he should correct his attitude.... but as mentioned above, they could not give him any examples, so he is a bit confused as to "how" to correct his "bad attitude".
Does he have any rights? He seems to think he is being set-up by co-workers that don't like him. Would this verbal warning have any merit?