can a guy use this bag?.....

Sure a guy can use that bag - it's not like there are ribbons and flowers on it (not like that should be a problem either :P). It's a black tote which seems pretty much a unisex bag.
 
I think if you can find a black guccissima tote.. that will be good.. but this patent leather kinda make it just little bid loud.. but again only my own opinion.. you will actually need to wear it to see it...

If you already have several messengers at home.. adding a tote won't hurt!