Hmmm, hunted up and down Oahu beaches for many hundred of hours in the dark and the daylight, in the water, on the shore, and in the sand, on crowded beaches and near empty beaches, around joggers, tourists, drunk teens, bums, kids, onlookers, and...
I've never had anyone run into me, throw coins, insult, mock, harass, elbow, block me, step-on coils, or otherwise do anything but ask polite questions. The worst I can say is excited kids can get in the way ... but that is it.
I'm going to guess it may be because I look like a normal fit and healthy guy detecting in a professional manner, dressed in a casual but not unusual manner, behaving in a calm, knowledgeable, responsible, friendly way that doesn't attract negative attention.
Now, for arguments sake ... If I were covered in camo like a for-hire mercenary looking like an unshaven bum, looking like a freak-show, swinging a cheap detector wildly like I'm having a fit, displaying no tact or skill, staring wild-eyed in front of me ignoring everything and everyone else as if finding money (i.e., greed) was your sole motive, walking too fast as if you are in a hurry to go somewhere else or embarrassed to be there in the light, and just looking like a disheveled, out-of-shape (e.g., fat) freak with no self-respect or understanding of the hobby you are apparently not even enjoying (what's the big hurry?), searching like a greedy weirdo for what? Pennies. Of course some people will interpret your presence unfavorably, perhaps fearing you simply because you are too strange to be reconciled with anything near normal or respectable.
If you project a calm, intelligent, professional, knowledgeable disposition... people will trust that though they don't understand your hobby they respect how you present it to them. Act like a crazy fool and you're likely to receive negative feedback from irritated people. Most people are considerate of others, at least until they see you as a threat. Consider the image you present the next time someone "accidentally" bumps you, or throws coins in front of you, or mocks you under their breath.