if ruach ra gets onto food when people touch it, then how come all food that is from a grocery store (which has inevitably been touched by Multiple different people including people who are not jewish and not orthodox, throughout the process of being transported from farm to shelf to cashier etc) .. why wouldnt it already have ruach ra on it?

for a few reasons that the food is permissible: 1. we assume that everyone who touched the food at least rinsed their hands in the morning before they touched the food. This weakens the ruach ra. 2. some hold that the ruach ra doesn't exist at all in our days. 3. we don't know for sure that someone touched the food without netilat yadaim. 4. Even food that was touched is not forbidden 'bedeeved'. See yabia omer (part 4, orach chaim 4), peninei hallacha tefilla 8;7) All the best