(Straight male) Is it ok to tell a friend that you know he is gay?

So I started indoor rock climbing about a year ago. it takes 2 or more people to climb because one person works the rope when the other climbs. I became friends with two guys shortly after I started and we climb all the time and some times takes day trips to climb, hike and/or camp. lets call them Dave and Karl. Dave and Karl knew each other for about a year before I meet them. from about the first day I climbed with Dave, he seem like he was most likely gay from the way he talked, some of the things he talk about and the way he acted around girls and the way girls acted around him. He would say things as if he was straight from time to time and it always felt kind of out of places. He once hurt him self at the gym lifting to much weight and I mad a joke. me-"were you trying to show off for someone" (I sad someone and not some girl) Dave-"no, it was 7am, there are no girls to show off to at 7am". he used "girls" when he could have just used "anyone" or something like that. when ever he says something like that I just want to be like "you know you can just be your self around me (and Karl). one reason why none has sad anything like this yet is we were never completely sure if he was or not but this weekend there were two big things. the first was he posted a photo of a deer on his facebook page and if you like in the brackground you can see that it was taking in a well know gay town at the beach (I don't think he relied that you can tell that from the photo). the other was when I was waiting for Dave to show up I started climbing with this new girl. when he showed up the 3 of us climb for the night. I took a short brake and just the 2 of them climbed for a little while. latter that week I climbed with just her. when we were talking I asked her if she thought Dave was gay and she sad "it was kind of dead give away when he was talking about his boyfriend". This weekend I was hanging out with Karl and I told him about this and he was like "I have known Dave for over 2 years and he knows this girl for less then 2 hours and he is ok "being out" with her but not me!". we both are fine with what ever sexual performance he is but we are kind of upset about being lied to all this time (and kind of badly at that) and that he does not think of us as good enough friends to be his self around us. some reasons we think he thinks it may not be ok being out to use is Dave thinks that we wont want to climb with him if we think he is "checking us out" on the wall (when guys climb it can be quite the show of flexing muscles and when you look at someone going up the wall you cant help but see there butt the hole time) (both me and Karl really enjoy looking at girls climbing because of this).So is it ok to tell a friend that you know he is gay?