I am so sick of their nonsense, they think that everyone has to follow their ‘Christian’ beliefs, or that the world has to go by their ‘Christian’ rules, Conservative-Christians need to get off their holier than thou attitude and high horse.
Examples of Divine Will for His People to cleanse the land and convert the world.
Amplified Bible, Classic Edition (AMPC)
16 But in the cities of these people which the Lord your God gives you for an inheritance, you shall save alive nothing that breathes.
17 But you shall utterly exterminate them, the Hittites, the Amorites, the Canaanites, the Perizzites, the Hivites, and the Jebusites, as the Lord your God has commanded you,
18 So that they may not teach you all the abominable practices they have carried on for their gods, and so cause you to sin against the Lord your God.
New American Standard Bible (NASB)
19 Go therefore and make disciples of all the nations, baptizing them in the name of the Father and the Son and the Holy Spirit,
Conservative Christians take these, and many other, passages as literal Cosmic Truth and see it as their divine duty to impose on others their beliefs. They ask themselves: If I saw a person in a house that was on fire, would I not do all in my power to save that person?
Of course they would. Anyone would.
Likewise, they see everyone who is not “saved,” according to their understanding, as being inside a burning house. They believe that in imposing their beliefs by preaching and witnessing they are literally saving people from hell, i.e. pulling them out of a burning house.
Hopefully that answers your question as to why they do it.
I understand your feeling that it is nonsense and self-righteous. However, they have an explanation for that too, and for any other rebuttal a nonChristian or nonConservative Christian can provide. Their explanations do not necessarily line up with real life or scientific discovery but they are convinced. For a deeper understanding of this phenomenon you may wish to research the findings of psychology of religion.