Myfriend nailed it.
What do you say when invited to wedding, held in a swanky country club, on a Sunday, and they order you a sealed, airline style meal (so kashrus is assured)to the invitation? I can’t make it because….. ?
Sure, you could make an excuse once, twice, a second time, But after a while, they see thru it and you look anti-social.
Think that’s a sticky situation? Hows this: You get invited to a mixed marriage. Do you go, and in effect, give this union your seal of approval? OK, this may not women in such a bind. But I(to the goyish velt) look very much like a Rabbi. In fact, more so than the “Brooks Brothers” rabbi who just performed the ceremony.
How do I get out of that one? Best bet: leave work at work.
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In the first instance one goes to the affair, is grateful for the thoughtful gesture of the host in ordering a kosher meal, and makes sure to congratulate the celebrants. In the second instance, one demurs going, explaining that while s/he wishes the young couple much happiness in life, given the very sensitive nature of the intermarriage issue, and given current Orthodox sensibilities, it would be inappropriate to attend. One then asks the host to please understand that it isn’t personal nor is it a matter of being judgmental. It’s simply a matter of religious sensibilities. Assuming one has generally been a mentsch until that point, and not inconsistent in his/her religious conduct at work, no offense should reasonably be taken.