If Catholics couldn’t patronize places that employeed sinners, we’d all be in trouble!
**Buying something from a place that has an employee who happens to have homosexual tendencies (which I am assuming you meant by all the above) is not wrong. You wouldn’t ask a clerk “Before I buy this, have you ever had pre-marital sex? Used contraceptives? Bought pornography?” **Just buying something from someone who committs immoral sexual acts is not supporting their sins, unless the item is used for sin (a dirty magazine, a “Proud to be gay” bumper sticker, etc).
Marching in a gay pride parade is supporting a sin, though. You are not supporting people with homosexual attractions as children of God, but celebrating and defending their sin. This is not loving or helpful for people struggling with homosexuality.