Earlier quoted context omitted.
I can't imagine writing this off. He's been seriously wronged, to the tune of quite a lot of money. The raise alone (promised in writing, never delivered) is probably substantial, considering it's been about a year since it should have happened. The tax issue seems less clear, but I have a hard time imagining you wouldn't be liable if you hid important investment details from a shareholder and therefore caused him a…
It doesn't really pay to win $50k in a lawsuit paying $30k on legal fees, plus the years it takes for the legal system to run its course. A lawsuit is a lot of stress. There's no guarantee he'd win. The corporation can be bankrupt when/if he wins. You can't keep working there after you sue them or your lawyer sends them a threat letter. There's no point continuing to work with dishonest people. Given their dishonesty…
If that is correct, at this point nobody wins. At best from his viewpoint, the company covers his tax bill (or I suppose establishes a new investment price a lot lower through bankruptcy or whatever). Much more likely is that he's going to have to weigh whether suing them and the likely payoff of that will be higher than the tax bill; hmmm, he'd better get a reading on whether he can pierce the corporate veil and go after them directly. Heck, he also needs to see if he can arrange a payment plan with the tax authorities, as others have mentioned; that bill will be due very soon, whatever the final outcome of a lawsuit is.
They're indeed snakes, the shares are indeed almost certainly worthless, but not for the purposes of his 2014 personal tax year :(. ADDED: unless, as others have pointed out, the investment was structured as debt instead of equity.
Yet another example why non-founder options/stock is frequently a negative.