The best answer to this is "yes." In other words, the "robber barons" were both good and bad.
The robber barons were good in that their efforts led to a boom in American manufacturing and other sectors. They built bigger and bigger businesses that were more and more efficient. As they did this, they built the foundation for a very prosperous (on average) economy. They also can be seen as good for the charity work that they did later in life.
The robber barons were bad in that they hurt specific people and groups of people as they built their businesses. They used tactics that could be quite ruthless to defeat competitors. They were also willing to condone violence to defeat workers who were trying to use unionization to get better pay and working conditions.
In these ways, the robber barons did things that were good for the economy as a whole, but they hurt various people while doing so.
There has been much debate as to whether the wealthy businessmen of the 18th century in America should be referred to as Robber Barons or Captains of the Industry. These two terms determine whether their actions are deemed to have been negatively or positive respectively. I acknowledge the fact that the businessmen were philanthropic and generously gave back to society. They also created employment for many people in the business dynasties they established. However, I disapprove of the tactics they employed in their pursuit for wealth.
They had no regard for their labor force which was overworked and underpaid. They were also corrupt and used their political networks to influence decisions in favor of their enterprises. In addition to that, they employed unethical predatory pricing in order to eliminate competition and establish monopolies that afterwards overpriced their commodities.
In conclusion, just like industrialization had both negative and positive implications, the Robber Barons were both bad and good.