"Should we blame Barry M. Goldwater for those 1968 deaths?"
No, we should blame him for dragging Conservatism from the cesspool of history to which the overweening greed of Wall Street, American labor, FDR and the New Deal had consigned it.  His candidacy and the passage of the Civil Rights Amendment handed the South to the Republican (we-ain't-racist-wink-wink) Party giving corporate entities the votes to free themselves from all legal restraint on the pursuit of profit.
Goldwaters' loss didn't end conservative aspirations.  They were heightened as the John Birch Society types saw their chance to rise putting pressure on Johnson to appease Right-wing chicken hawks so that we not only ended up deeper into Vietnam but with Tricky Dick Nixon who dealt the fatal crack in the American Experiment from which slithered Donald Trump, hell-bent on finishing the job of splitting America apart.  Even if impeached the fools who elected him remain committed to suicide and will find another enabler.