many branches have evolved to be more accepting.

Yet for some reason we aren't allowed to blame the one that hasn't

Well, to look at the shooter's own Imam (Syed Rahman) from his childhood Mosque, I'd argue the opposite.

He's utterly denounced the act from multiple news sources.

Like here:

"It might be some psychological problem or some anger at direction with somebody because, if this is his mosque, we never promoted any kind of extremism," Rahman said. "He might be radicalized by the Internet."

And here:

"As for the horror Mateen unleashed, Rahman said, “I condemn it, and I disown it. This is our country. This makes it very hard for us.”

In fact, it seems as though Rahman was on the money with regards to being radicalized over the internet:

“It is no coincidence that this happened in Orlando,” said a law enforcement source familiar with Robertson’s history of recruiting terrorists and inciting violence. “Mateen was enrolled in [Robertson’s online] Fundamental Islamic Knowledge Seminary.”

Now if you click on the article and continue to read onward, you'll notice this:

"Robertson's school may not have been the only source of Mateen's spiritual guidance. The gunman was at the Islamic Center of Fort Pierce with Imam Shafiq Rahman two days before the nightclub attack, according to The Washington Post. That mosque was frequented by American-born suicide bomber Monar abu Salha, who blew himself up in Syria in 2014, and the two knew each other, according to officials. Mateen's association with Salha led the FBI to interview him in 2014. Rep. Michael McCaul, chairman of the House Homeland Security Committee Mike McCaul told Fox News law enforcement determined at the time their contact “was minimal.”"

Which, again, disproves his own spiritual upbringing (by association) influenced by his childhood mosque.

.

, even though the shooter outright told the world why he did what he did.

You're right. He pledged allegiance to ISIS. Which is both an extremist and comparably small faction of Islam, not widespread in terms of population by any means.

"Mateen was, however, a devout Muslim beholden to the scriptural mandates of Islam. He reportedly pledged allegiance to ISIS during the massacre in a phone call to police. The FBI suspects that he was motivated by jihadism."

.

Even though we have video of the imam from the Orlando Mosque saying that homosexuals deserve violent death.

Ah, yes. This guest Imam? Who is similarly a fundamentalist?

"Strict Islamic purist groups, like ISIS, follow the letter of the law and carry about these Quranic mandates regularly. For months now, the Islamic State has publicly executed alleged homosexuals by throwing them off of ten-story buildings and then stoning their bodies."

.

Fundamentalism is by its very definition opposed to the evolution of ideology. To cite one data point and use it to draw a line-of-best-fit can drastically skew the context, re: the guest Imam.

It ignores Florida's Imam Muhammed Musri:

"On Twitter and Facebook, Musri wrote: “On behalf of American Muslims, I want to express our outrage and shock of the mass shooting in DT Orlando, FL. Our thoughts and prayers are with victims & their families.”"

It ignores Mateen's own Imam Rahman:

"Yusufiy said she was "devastated, shocked, started shaking and crying" when she heard about the shooting, but she attributed the violence to Mateen's mental illness, not any alliance with terrorist groups.

Rahman agreed.

"My personal opinion is that this has nothing to do with ISIS," he said."

It ignores a gay Imam, Imam Daayiee Abdullah:

"he said, “I can’t deny some Muslims do” have a serious problem with gays, and that some Muslims have been taught that gays need to be punished or even killed. ISIS has murdered homosexuals, and five Muslim countries (out of more than 50) still have a death penalty for homosexuality on the books.

“The actions of ISIS in killing gays is fueled by a perverted understanding of Islam. An understanding typically learned by word of mouth, not an actual reading of the text and understanding of the principles of Islam,” Abdullah added."

If this hasn't made my point, I don't know anything that will at this time.

EDIT: I don't intend for the examples of Imams at the end to be sweeping, although I'm sure there is more evidence for both sides. Frankly, I can't be arsed to discuss much more considering the situation in general, let alone the fact that it feels too soon being so close to it all. I'd be content to settling with "This is a problem, lets work toward a solution" at this point.