As a thought-experiment, suppose you have a society in year X in which a substantial majority of people are opposed to putting resources into some project.
Time passes, it is now year Y and an individual has managed to amass control over sufficient resources to at least begin this project.
More time passes, it is now year Z and the project requires further investment. The individual who initiated it seeks public funding to continue the work?
1. is it appropriate in a democratic society that an individual can direct resources on a large scale into projects rejected by most people in that society?
2. should the society consider funding the continuation of the project?
If the answer to (1) seems immediately clear to you, consider your answer in the case that the project is "Invade our largest neighboring country" or "Develop new bioweapons that will only affect people of a certain genetic makeup" or even, somewhat realistically, "Develop ways to burn fossil fuels on sufficient scale to alter the composition of the atmosphere".
What is the qualification possessed by the very rich, other than "well, they're rich", that should entitle them to make such decisions?