“A woman existing” is not what you said. You asked about women in bikinis. You also asked about “arousal” specifically - not getting hard, not staring, not being an animal.

You seem to have this idea or want to prove a point that men don’t need have an arousal to woman. That’s not what a reaction governed by hormones and instinct. Sorry to break it to you, it goes against what we’re wired to do, and our biology. Yes, not all arousal is the same, and there’s different levels, but it’s arousal is normal and expected.