The reason it is gonna hurt photographers is not because they have to pay the sales tax, because they don't, its because they have to collect sales tax from their clients.
Its already hard enough to sell photos (this is coming from someone who is trying to) these days, with all the hobbyists out there who are willing to give their shit away for free. This makes it more difficult since now businesses will have to pay an additional tax on top of the photographers price; which will encourage them even more to go affter the more mediocre, yet free shots from the hobbyist who just got a kewl new dslr.
From the outset this does not seem unreasonable, especially since everyone else is required to collect sales tax. However any time you increase or add a tax to an economy, it takes a hit.
Right now, photographers, like everyone else, are struggling to maintain their businesses and income, if not more so. Increasing the taxes involved with photography will cause many clients to look for photographers outside of Utah. This will push many photographers to leave Utah, pulling even more money out of the state's economy, as it becomes less attractive for photographers to work there.
If the photography industry were booming right now it would be a different story, as many photographers could simply look for another client who was willing to pay the extra taxes, instead of struggling to hold onto their current ones.