Dear Khaleel Saudagar,
The major issue found in your post is maligning the image of the HR Head on social media by the terminated employees. However, this activity has nothing to do with the Trade Union Act. It has to be handled separately. The HR Head may consult the company's legal team. They are the right people to guide him.
Since the HR Head's image is tarnished in social media, that does not mean that it is his personal problem. For the misconduct committed by the office bearers of the trade union, he had used his positional power in order to enforce the discipline in the company. Though the terminated employees are personally targeting him, the company should take up this matter on his behalf. It is not his problem, but the company's. Therefore, legal team of the company cannot remain a mute spectator to the maligning game being played out by a few unscrupulous ex-employees.
Your company has two options. The first one is to take legal action. The legal team may file a police complaint. Let the police pursue this case. If this option is exercised, then the plaint will be between a company and the ex-employees. This will help in keeping the HR Head out from the litigation. In the future, he may quit the company or even retire, but the case could continue.
Nevertheless, in India the court cases move at the slowest pace and filing a suit is a headache in itself. Therefore, the second option is to wait for a while and check whether or not the terminated employees cool down. Right now they are reacting. Every reaction need not be retaliated with the reaction from our side. Give them some time to subside their anger and possibly they may mend their ways. However, if they persist with their wayward behaviour, then the option of filing a police complaint can very well be exercised.
Dealing with the members of a labour union is always a challenge. It is more so for the office-bearers. Nevertheless, the HR Head rose to the occasion and by initiating disciplinary action, he has shown firmness to institute a culture of discipline in the company. Now it is time for the company to rise to the occasion and show firmness of equal measure by backing him. He cannot be left alone to fend for himself.
By the way, coming to the post itself. Are you the HR Head in question but have written the post as a third party? Whether you have written on behalf of the HR Head or otherwise, the noteworthy factor is the requirement to raise a post on the public forum. Generally, the people who accept the position of the HR Head in an unionised company are seasoned ones. They cut their teeth while dealing with the labour unions during the early stage of their career. In your company, has the HR Head not acquired competence through trial and experience of dealing with the labour unions?
Thanks,
Dinesh Divekar