The meme/picture shit usually on social media is stupid but the message I think it's trying to convey is tolerance.
It's kind of an interesting situation. I don't know how someone who doesn't support homosexuality can be friends with someone that is gayl, friends require support, if you don't support their homosexuality, that's not a friend and I don't think the gay friend will want to be associated with one that is simply tolerant.
However, when it comes to strangers/in general, that's a bit different.
Tolerance in acceptance of a lifestyle or view one might have, meaning they won't oppose homosexuality but won't support it because it goes against their own beliefs/views. However it is a fine line with the status-quo.
Not once in human history has anything ever had all agreed upon view regarding social issues, religion, etc and I think it's improbable that'll it ever happen. The best way in society to treat each other is tolerance which is what that image means.
I think it's the only viable way society can deal with itself, if you truly do not oppress, do not support anti sentiment of an issue, etc, I think that is fine. You don't have to support an issue, you don't have to agree with it if it goes against a belief you may have, but you have a responsibility then to not aid the status-quo or oppression, in other words if you see someone being homophobic, you should confront that behaviour even if you disagree with the lifestyle or view because if you don't it goes against some of the values of tolerance - you should confront bigotry.
I support LGBT, I'm not gay but if I were I wouldn't want someone who doesn't support me in that way to be a friend, and that goes for anything, if you're simply tolerant and won't support (in terms of friendship), that's not a friend to me.