So let's assume you have a raging foot fetish .... if only they were attached to a cute girl, I'd go crazy with those!
Have you ever had a moment like that?
I wouldn't describe my foot fetish as raging, but it's definitely a strong one, especially when linked with tickling and I most certainly have taken notice of certain male friends' feet and observed qualities in them (as well as faults) just in the same way as I do with a ladies feet
But with regards to going crazy with them, I don't think "if only... ", I just think "well, why not?" - on the basis that I've concluded that the feet are in good condition and attractive to me, then they are therefore tickleable, so I'd proceed to tickle them if the chance is a suitable one (or if not, I'd just think about tickling them some other time in the future).
A foot is after all just an everyday body part. If you can mentally get past the sexual link you may have with tickling and just enjoy the fun aspect of it, or instead try to focus on the sexual turn-on for tickling as a overall kink, rather than get hung-up on the need for gender-specific tickling, you can have a lot of fun tickling your male friends feet.
If it came to armpits, stomachs, backs etc and they were blatantly on display under my nose - I'd find it harder then to bring myself to tickle them, as to me these are areas I associate more with intimate physical contact, which is something I'm only interested in sharing with a woman - so, if anything, it's usually only close male friends and very quick tickles.. but with feet, whole different story!