It sounds like you're saying you don't like the way they look. I don't like the way they smell, and that's not being snobby, but it seems it's not being smart. Natural insect repellents are surely a good thing.
You're right . . . if tomato whiteflies were a problem in my garden, I might embrace marigolds - unless I could find an alternative control such as a spray containing limonene that is. It seems that a citrus extract containing limonene was formulated in 1998 to combat mealybugs and scale insects but I can't tell if there is a product on the market today that has limonene as an ingredient. Limonene, a citrus extract, for control of mealybugs and scale insects. - PubMed - NCBI Further research into ways to control white fly led me to this website: How to Control Whiteflies | Planet Natural which lists a number of ideas. I'm puzzled why #9 says, "Fast-acting botanical insecticides should be used as a last resort . . . " since this would probably include the chemical in marigolds - limonene. Given the research shared by Junglekeeper, marigolds themselves ought to be mentioned on this and other lists - cheap, safe and effective.