I'll need some more context on that....not sure how a Supreme Court ruling on gay marriage had anything to do with an invasion of Serbia.

The only Supreme Court case with relation to WW1 has to do with the legality of the draft that I know of.

I've literally no idea what the guy could be talking about... Maybe something about Schenck vs US....? I'm trying to make some leap between gay marriage, Schenck, and the first amendment... But the decision was after the war, anyways. No idea. The guy is probably your typical crackpot.

He may have been referring to Woodrow Wilson's approach entering WWI (although I could find no corollary Supreme Court ruling) and to the treaty that ended WWI. I've heard several other people who practice conservative politics analogize the two with this recent Supreme Court case.

Wilson was elected initially on promises to maintain US neutrality in WWI. Circumstances changed that position after he was elected, and he chose to ask Congress for a declaration of war.

At the end of the war, Woodrow Wilson's had strong opinions about how to conclude, outlined in his Fourteen Points. It was seen by many (especially outside the country) as being too lenient on the Germans. The final treaty to end the war, the Treaty of Versaille, is seen as an (ineffective) hybrid compromise of Wilson's points combined with the more punitive terms favored by countries like France.

How does all this relate to the recent Obergefell v. Hodges case? From some political perspectives, it as seen as the start of another slippery-slope situation. The decision to enter WWI led to significant growth of women in the workplace. As women gained more influence and independence, they eventually drove passage of the 19th Amendment to the US Constitution, granting women the right to vote.

By similar measure, the Treaty of Versaille established the League of Nations. It was poorly conceived and implemented, but it did lay the groundwork for the later emergence of the United Nations as an international political force.

Politicians of the time, in particular Republicans led by the notably conservative Henry Cabot Lodge, opposed the US entry into WWI, the creation of the League of Nations, and the approval of the 19th Amendment, which extended suffrage (the right to vote) to women. There is currently debate, among those of similar political philosophy, about whether Obergefell v. Hodges leads to the same sort of political empowerment for LGBT constituents.

Of course, I can't say for sure that this is the frame of talking points that you overheard, but it is certainly a frame of reference that is emerging after yesterday's decision.