Highly simplified example: if you spend $100 million over five years on inputs, all while receiving no revenue, and then sell your gargantuan output product (say, a mega-robot) in the sixth year for $100 million, then you haven't yet made a profit -- even though your books show a $100 million profit in the sixth year. Paying no taxes in that year would be reasonable.
If anything, my understanding is that corporate tax law is unusually harsh about such long-term projects, limiting how many years you can carry forward losses.
The specifics of how they got to $0 taxes matter, and not all reasons are shady. Some are, of course, like deducting arbitrarily high IP licensing fees to your foreign sockpuppet subsidiary. In that case, sure, hit 'em with both barrels.
But please, attack them for the right reason.