How does it in any way harm a straight person if a gay guy opens a bank account at Citibank?<<<
It doesn't harm any straight person like a slap in the face or something - it's all a matter of the "company one keeps".
To go with the Citibank example, I'm sure there are plenty of gay people with accounts at Citibank. I, too, have an account at Citbank. In what way have I been effected, in any way, by the fact that homosexuals have checking accounts at the same financial institution?
How are my checking, savings and investment accounts effected one bit by Citibank's renting a booth at this trade show?
You might want to boycott everything, because I am sure much of what you own, so does some gay guy or lesbian.