Most people who listened to the Pope's speech to Congress were probably waiting for him to touch on such subjects as inequality, climate change, homosexuals, priest sex scandals, or maybe some other subject.
However, Pope Francis used his strongest words for a topic that doesn't get much attention in the United States, but should.

Here we have to ask ourselves: Why are deadly weapons being sold to those who plan to inflict untold suffering on individuals and society? Sadly, the answer, as we all know, is simply for money: money that is drenched in blood, often innocent blood. In the face of this shameful and culpable silence, it is our duty to confront the problem and to stop the arms trade.

This isn't the first time that Pope Francis has spoken out against the merchants of death.
In June he called out arms investors as hypocrites.

"It makes me think of ... people, managers, businessmen who call themselves Christian and they manufacture weapons. That leads to a bit [of] distrust, doesn't it?"

A month before that he called the weapons trade an "industry of death".

You can't get much more clear than that.

You might say that the Pope was speaking in the belly of the beast.

The United States is the largest exporter of weapons in the world, and has been for a long, long time. The USA sent major weapon systems to at least 94 countries in 2010–14, nearly twice as many countries as Russia, the #2 arms exporter.

We exported $23.7 Billion of instruments of death just in 2014. Under Obama, weapons sales have hit new records, having increased 23 percent from the 2005–2009 years.
Congress, of course, has been more than happy to go along with this, since they are major recipients of campaign contributions from weapon suppliers (i.e. legal bribes).

This June the Obama Administration lifted a ban on arms sales to Bahrain, despite their human rights abuses.
In August the State Department agreed to speed up arms sales to the Gulf nations.

Those weapon sales are going to places like Saudi Arabia, which happens to be using them right now to cluster bombs on civilians.
What the Pope has done is point out the moral culpability that the United States has in flooding the world with tools of death.

The recognition that arms sales can result in the spilling of “innocent blood” for profit is a far cry from the cover stories so often used to justify multi-billion-dollar arms deals — that they promote “stability” and are only for “defensive purposes.” As the country that reaps the most money from the international arms trade, the United States bears a responsibility to take the leadership in curbing weapons trading around the world. A good start would be to cut off U.S. supplies to Saudi Arabia until they stop engaging in indiscriminate bombing in Yemen, which has caused a humanitarian catastrophe of the highest order.