I'm not saying you should tell him this, as it would just piss him off. However for your own edification...
Those who would encourage Armageddon in the hopes of hastening the return of Messiah are doing the work of Satan. This battle in the valley of Mt. Meggido is the natural consequence of sin and evil, and the rejection of God's will. To encourage evil is evil.
The scriptures speak both of how we should walk in the days of evil, and how even though God can bring good from evil that we are not to encourage or do evil so that good may come. The Ephesians citation is background, and the Romans citation is directly on point.
Ephesians 5:15-17 "Therefore be careful how you walk, not as unwise men but as wise, making the most of your time, because the days are evil. So then do not be foolish, but understand what the will of the Lord is." [NASB]
Romans 3:5-8 "But if our unrighteousness demonstrates the righteousness of God, what shall we say? The God who inflicts wrath is not unrighteous, is He? (I am speaking in human terms.) May it never be! For otherwise, how will God judge the world? But if through my lie the truth of God abounded to His glory, why am I also still being judged as a sinner? And why not say (as we are slanderously reported and as some claim that we say), “Let us do evil that good may come”? Their condemnation is just." [NASB]
Note that in the days of evil, believers are called to be circumspect and wise. That we are called especially to understand the will of God and do it, and not to be foolish.
The person the OP referred to is being foolish, because he forgot that we are specifically told NOT to do evil so that good may come. That even though goodness may be brought out of our evil, we will still be held to account for all the evil we have done.
The person the OP is referring to is encouraging the advance of evil, the Armageddon, because he thinks that the return of the Messiah will come from it. In doing so with the full knowledge that he is intentionally encouraging the Armageddon...a fuller intent than most who perform the same actions...he will be held to the same accounting as those who bring about the Armageddon with the intent to defeat God. The purpose to bring good from the evil is irrelevant, the intent is the death of millions of souls and he will be held accountable for that.
The Armageddon will come when it is supposed to no matter WHAT we do or do not do. Believers are called to continue "redeeming the time" and doing good even if we have the full knowledge of what we are up against. We should be working to live out the will of God up until the very instant He comes back for us. That means, of course, electing a President who will carry out the Golden Rule and make America that shining city upon a hill.
Doing evil do that good may come is just as evil as doing evil for evil intent. It's all equally evil. The scriptures make that abundantly clear, and the person referred to in the OP has lost the path and is clearly wandering in the wilderness.
To the OP, I'm not sure how you could reach him. Perhaps discuss the quoted section from Romans? It will be particularly difficult. Nobody wants to be told they are working for Satan... So if you try you may not want to mention that part...