Alma knows about Ennis and Jack right back from the time of the four year reunion - we know that from the scene at Thanksgiving when she confronts him about it. She knew for all those years, but she never told anyone, never said anything when she could have ruined Ennis, but she didn't. That says a lot about Alma as a person. Was it to protect Ennis? Was it to protect the girls? Maybe she was simply trying desperately to save her marriage, because after all she does love Ennis. She refers to Jack as "Jack Nasty", but again I don't think that's because she's homophobic (again, we're not privy to her thoughts either, and we're given no indication either way really) but more that Jack's the person who in her eyes "stole" her husband away from her. Even after the Thanksgiving scene though, there's still no indication that she tells anyone. Ennis still lives in or near the town, and is still finding work in the area, so there's no indication that anyone knows Ennis's secret.
I don't think there's any indication at all that Cassie knows anything about Jack, or even suspects, so I don't think that Cassie would be a danger to him, even after they break up. Alma certainly could be a potential danger to him, but as I said, there's no indication that she says anything to anyone, and though I suspect the fact that she could potentially tell is something that's a constant worry to Ennis, I think that they probably came to some kind of uneasy truce.
Such murders of gay men still happen in our societies, unfortunately, just because they are gay men !! The case of Sheppard is one !! And many murderers get away with it - (I know of one in my last city who never spent a day in jail since the jury believed him and felt sorry for the murderer... of all things !!), or a murderer just spends few hours in prisons! But the dead can not talk... and neither can his relatives nor loves nor others talk to him now !!
I fear nearly daily getting to be discovered as a gay man, and getting murdered because of that orientation !!
I have lost jobs, reputations, health, a house and property, because I am a gay man in our democratic societies !! And I fear the islamics and other such radicals coming into our lands, since many would be proud to murder a gay man !!
So Ennis fears and much more, since even for his life !!
As you say, that such murders still occur today in the twenty-first century in a supposedly enlightened society is a tragedy, and that gay men, such as yourself, must fear the consequences of their sexuality becoming known is something that shouldn't happen. We live in an imperfect world though, and sadly society has alsorts of prejudices and faults. I do fear though the demonising of the Islamic culture. My background is in working in equal opportunities, and through my work I have come into contact with a lot of people from different cultures. The majority, even if they don't always share all of our "western" beliefs and customs, would never condone murder and such acts of violence. To brand all Muslims as radicals, extremists and terrorists is like saying that those involved in the Waco siege (Seventh Day Adventists are a Protestant Christian denomination) are representative of all Christians, which simply isn't true. Numerically religious extremists make up only a small minority of those within religions. Branches of different religions all over the world have extreme views, and not all radicals and extremists form their ideologies based on religious views.
The British National Party in the UK is an extreme right-wing political party whose main policy is of returning the UK to a "overwhelmingly white makeup of the British population that existed in Britain prior to 1948" - they don't accept the Jewish, Hindu or Sikh, or Muslim religions to be culturally or ethnically British. Under their previous leadership their policies were largely anti-Semetic, but their current membership focuses on Muslims. They have anti-homosexuality policies also though and have a policy of re-criminalisation of homosexuality, and advocates the repeal of
all anti-discrimination legislation.
They often are linked to violence and intimidation (such characters are portrayed in parts in the film "My Beautiful Laundrette" about a gay relationship between two young gay men, one white and one Asian - ages since I've watched that actually - I might watch that tonight) and they have also been linked to terrorist groups. The BNP's philosophy isn't based on religion, but they can be just as dangerous.
Prejudice and intolerance exists in all sorts of forms and in all segments of society still today, whether in rural Wyoming, or inner-cities in the UK, Canada or the US, and homophobia is still very much alive similarly, and is something we should all be fighting.