A no dilution privilege is precisely that, a privilege and not a duty. There is no reason to believe the shareholder is being greedy, after all, they are adding risk to their own position at the same time. A no dilution privilege only gives the right to maintain a constant percentage, if there are no resources to protect or maintain that right then it vanishes as if it did not exist.
"Full consensus" is not a well-defined term. Hopefully, the articles of incorporation define what that means exactly or it will simply be a majority-rule based decision.
Unless he is the majority shareholder and controls the board, then he cannot force the shareholders to dilute. If he is the majority shareholder, then it was foolish to enter into a written contract regarding the firm when informal understandings and ideas mean nothing legally. If you believed you were going to be protected, but are not, then the lesson is to hire a good attorney to explain fully the set of scenarios that could happen in the future.
Things like this are very common with angel investments and venture capital investments. Indeed, they plan for it. If they insisted on the no dilution agreement, now you know why.
The only control you could have is to get a majority of the existing shareholders to refuse to expand the company and to choose a board that will support your interests.