If a Christian does not want to attend an incorporated church because he says it's wrong, is it right for him and his wife to worship alone on the Lord's day because he says an incorporated church is in sin, and he cannot find a church that is not incorporated?
A person cannot decide what is or is not sinful. That is something that God alone teaches. To claim it is wrong for a church to incorporate, he must first prove who such action violates the Scriptures.
Governments exist by the authority of God (Romans 13:1-2). So long as the demands of a government do not violate the laws of God, there is every reason for Christians to be obedient to the government under which they exist. When a congregation owns a building, the government requires that there be someone designated to own the land, whether it be one or more individuals or a corporation. The preferred method is a corporation because people come and go. The existence of a congregation generally exceeds the life of people. If individuals owned the property for the church it would have to be bought and sold as the people came and went. If someone died while owning the property, it would pass through that person's inheritance. Such is both annoying and costly. Having a corporation own the property is more expedient under United States law because trustees can be named to fulfill the legal requirement and they are easily changed as time passes.
There is nothing in the action of incorporating that conflicts with God's law. It does not give the government any power that it did not already have. It doesn't take away any authority that a church has.
Therefore, to decide to not worship with the Lord's people because an individual doesn't like the fact that the church is complying with a government is foolish because it places an individual's preference over what God has said.