The more I think about it, the more I think someone could only see this as 'wrong' if they have a rather strange attitude towards bodies and clothing in the first place.
It's entirely ok not to like the bikini- personally I think it's bleurgh- but then I could say the same for the shorts over sparkly tights or the over the top shiny party dress I've seen our neighbours kid in recently.
And personally I used to dress my kids in over sized t shirts on the beach, because I'm very careful about sunburn and also I think a loose piece of clothing is actually more comfy than none
But to say a bikini is 'wrong' is just weird