You can notice and admire cock and still be 100% straight. It's about how men are put together sexually... we are lookers, and if it looks like sex, we are interested, even if we don't actually want that particular brand of sex.
Example: Anybody seen dogs or horses fuck? You look, right? You might even start to get hard. But do you want to go out and bang a dog or a horse? No. Cause what got you interested was just the sex.
Looking at dogs hump is not the same as wanting a dog. If you are a man, sex is interesting. And big cocks, like sweet breasts or a nice ass means sex. Period.
Now, if you want to reach out and touch it... that's different. Come talk to me.