It isn't directly an issue of morals. I was speaking to the severity to the individual employee. Opposition to gay marriage is obviously a hugely important issue for a gay person. There is no way to really compromise on a civil rights issue like that. Either people have equal rights or they don't. Someone being excluding from those rights can't accept neutrality as an answer.
Also I want to point out that I specifically called the argument unreasonable and not the people. I meant "unreasonable" as a synonym to illogical. There is no real logical consistency to any arguments that there should be added legal benefits for straight couples that don't apply for gay couples. All the arguments fundamentally come down to some sort of bias against gay people which can be ideological or spiritual but are never based on reason or logic.
I think you've just never been exposed to any counter-arguments, frankly. The media won't do it so you're left to believe anything you disagree with is completely irrational.
The rational/logical argument for opposing gay marriage has two strands:
1. Marriage != civil unions. You can have equal legal rights without the religious concept of marriage being involved, and many countries already had that, so the effort to go further in many places didn't involve doing anything beyond upsetting religious people. It didn't make the lives of gay people better in any specific legal ways. You seem to be conflating the two.
2. The historical taboo against homosexuality is because such couples don't produce children, and thus must be supported in old age or times of famine etc by the wider community who may not feel any particular loyalty to them. In a world where the family is the primary unit of support, such couples can end up with nobody to support them, and moreover, don't contribute to creating the next generation.
The concerns in (2) may seem parochial given the existence of the welfare state and contemporary concerns about over-population. But although it's a sad and scary prospect, it won't be a huge surprise if homophobia comes back in future generations because the demographic deficit is enormous and nobody's talking about it. The welfare state and pension schemes depends critically on a growing and strong economy to support it, which boils down at some level to having enough people. Yet birth rates are far too low to sustain those systems over the long run. If pension funds start drying up because there aren't enough workers, then gay couples might end up being hit by a doubly whammy of (a) not having children who can support them if the state fails to do so and (b) popular resentment against them for contributing to the problem of a declining population.
Of course, neither problem would be their fault. They didn't choose their orientation. However, people certainly knew that centuries ago and the taboo existed and was propagated because society needed families and a growing population to be stable. If pension funds are in as much trouble as demographers claim, we may see a return to that world, and it won't be entirely irrational.
Also I want to point out that I specifically called the argument unreasonable and not the people. I meant "unreasonable" as a synonym to illogical. There is no real logical consistency to any arguments that there should be added legal benefits for straight couples that don't apply for gay couples. All the arguments fundamentally come down to some sort of bias against gay people which can be ideological or spiritual but are never based on reason or logic.