I was similarly curious about that whole sentence. My sense among people I know is that LBGTetc are not particularly underrepresented in tech; and are possibly overrepresented. (Once you correct for the overall underrepresentation of females, that is; lesbians are clearly underrepresented, but not clearly so once you limit only to women in tech.) Like you, my evidence is only based on my personal interactions with people, but I would certainly like to see some numbers supporting the claim.