[Umfuld]

The very same people trying to redefine society

I know. Those very same people who got women the right to vote. And thought it was wrong to own other people as slaves. The b*st*rds!

Is it bigotry to think that a young child needs a father and mother as both provide different yet necessary functions for a developing child

In this context, yes. Very much so. Because marriage and raising a child have nothing to do with one another. It's looking for a reason to justify bigotry.
My best friend is married, yet her and her husband have no intention of having children.
If you feel this way, should my friend have been allowed to be married knowing they weren't going to have children? Yes or no. Don't dodge this, give a yes or no answer. Answering YES dismisses your point completely.

Is it bigoted to point out studies which show children develop better with the traditional setup

Link?

Is it bigoted to quote a marriage definition from a source such as Merriam Webster

It was a meaningless post. As the law being discussed seeks to change this. The dictionary is only stating what the unjust law says.