write you congressman about holding a trial for this guy...

He was Wicked.

People were executed for far less than that in the Old Testimate. And it'd be redundant to hold trials when the actions are being done by a (usually) all knowing god.

Relative to all those the 'LORD put to death' in the Old Testimate, I don't see anything wrong with this particular scripture.

~
P.S,
Is it Testament? That doesn't look right to me. But Testimate always sets off my Firefox's autocorrect. I've probably been using an incorrect spelling this whole time.

Its a very important and valid point what you refer to.
many atheists say God is cruel and mean, a destroyer and dangerous.
In light of the global flood one mans death is seemingly irrelevant, though its not. As stated Er was executed for sin, sin is against God and will be punished. Destruction is the outcome of sin.
That little event listed is the whole story of mankind.
Sin then destruction.......obviously as we move in to the New Testament we find Jesus becomes our redemption from destruction.
Great biblical story in those few words

Here's a better one. One of my favorites to cite.

2 kings 2:24
He turned around, looked at them and called down a curse on them in the name of the LORD. Then two bears came out of the woods and mauled forty-two of the youths.

No "Trial". What happened was that a few innocent kids mocked the wrong person for being Bald, so God sent bears to tear them into pieces. Not just the few mockers, but a total of 42 children, the others killed for being "Guilty by association", or just so God could make his point.

Or, everyone killed in the Flood. Babies, Children, Pregnant Women, Kittens, Pandas. Do you think they all each were given a trial to see if they deserved death?

I can't even think of any cases where 'God' did hold trial for people he killed. Some deserving to die and some not. However, in the case of Er, there's a vague justification for his being put to death. The "Wicked" thing could mean a various amount of death worthy offenses.