As a seed investor and VC investor I'm happy to inform you that it very rarely happens that seed investors or VCs have a controlling interest in the company.

You may have a board seat. And if you don't like what the company is doing your most powerful move is resign from the board. Another option is to force a shareholder vote, but if the founders still hold the majority (as they should, at this phase) that will be overruled.

I'm freshly amazed by the lack of basic corporate law knowledge in the context of HN, this is really something that should be known if you partake of conversations like these.

I agree they should respond appropriately, but depending on what happened that response may not satisfy you.