They're supporting Trump because they've been failed by the status quo, and Trump has, at the very least, recognised that, versus the establishment who just pretend everything is OK.
His 'fixes' for the economy aren't the typical progressive economic fixes, but rather populist ideas like strong-arming corporations into keeping American jobs or keeping money in the US which, while not necessarily drastically reducing inequality, will have the result of at least giving some of the working class a boost. Globalism absolutely has allowed many working class jobs to be outsourced to areas of cheaper labour.
Whatever you think Trump is, he's a result of the sentiment of his supporters. He's the least-ideological Republican candidate in recent history (which is why Ted Cruz campaigned on the idea that Trump isn't a 'conservative').
> if he loses I fear things may get violent.
Things are already violent. Look at the news, riots in multiple US cities. Violent protests everywhere. Mass swaths of unemployed people who resort to crime. These are all the result of failed economic policies.
You're right though - if the status quo continues, the violence that's occurring today likely will escalate.
" The average income for the richest 1 percent of Americans, excluding capital gains, rose from $871,100 in 2009 to $968,000 from 2012-13, he wrote. The 99 percent, on the other hand, experienced a drop in average incomes from $44,000 to $43,900, Wolfers said. The calculation excludes government benefits in the form of Social Security, welfare, tax credits, food stamps and so on. "
From http://www.politifact.com/truth-o-meter/statements/2015/apr/...
However, the research in Piketty's book also shows this up through 2010, and I remember the figures he was drafting showing 50% of new income going to the top decile going through 2010 - so Bernie might be a bit aggressive in his numbers, but even 50% of new income going to 10% of the population is just bad. I remember in the book he outlined how only places like Colombia or otherwise Fascist regime countries are worse than the US.
I can dig up the numbers from the book - I read it on ebook so it's always a hassle waiting for the pages to refresh looking for info :/