What does Hawkeye's dad think of BeejHawk?
i'm sure others have more insightful or nuanced takes on this, but i have given this some thought before!
despite the time period and its associated homophobic views, i have a somewhat optimistic view of how daniel might react to the reality of beej and hawkeye being in a relationship. i have a few reasons for this:
he raised hawk, who turned out to be—while flawed—an intelligent, curious, compassionate, and politically/socially progressive man. given how close they are, it's likely that daniel shares many of hawkeye's values, if not outright helped imbue him with those values at a young age.
he raised hawk, and i imagine young hawk was all the things he is as an adult: largely uninterested in displays of masculinity, very emotional, and unwilling to conform to some of the strongest societal norms of the time. we have no evidence to indicate that daniel has ever rejected hawk or tried to redirect him toward more "normal" behaviors when he was young; perhaps daniel loved him even more fiercely because his son was a little different. and if that's the case, daniel seems more likely to accept hawkeye and bj's relationship than most.
only a few episodes into season 4, when daniel receives word that hawkeye is dead, he calls and asks specifically to talk to bj. not potter, not any of the people hawkeye's been telling him about in letters for months on end... only bj. daniel seems clued in to hawkeye and bj's bond early on even though they've only been friends a short time, and, most importantly, daniel trusts bj's word over anyone else's. hawk likely wrote to daniel with stories about bj all the time, and i think a lot would fall into place for daniel if he were to find out hawk and bj were in love.
all that said, i don't think daniel is exactly jumping for joy at the prospect either. hawkeye being in a relationship with another man is not only socially unacceptable, it was punishable by law. there are serious repercussions if they're found out, and i think daniel would be deeply worried about his son's future.
but ultimately, when he sees the veil of war over hawkeye's eyes lift for just a few moments while he recounts a story about bj, or when he finally meets beej in person for the first time and notices the way hawkeye looks at him (maybe even the same way his late wife looked at him), daniel might feel some kind of relief knowing that they have each other to lean on, that bj can bring out the best in hawkeye, that bj makes hawkeye happy—and daniel understands if nothing else.