Secular Humanism does not require belief in a supernatural deity. It makes no supernatural claims. Promises no wish thinking regarding afterlifes. Casts no aspersions upon others who believe differently.
That does not insulate it from misuse. Nor is it free from casting aspersions on others who disagree. For instance, let's look at the Humanist Manifesto III
Humanist Manifesto III:
"Humanists ground values in human welfare shaped by human circumstances, interests, and concerns and extended to the global ecosystem and beyond. We are committed to treating each person as having inherent worth and dignity, and to making informed choices in a context of freedom consonant with responsibility."
This has the possibility of misuse by subordinating human freedom and dignity to "concerns and extended to the global ecosystem and beyond".
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Knowledge of the world is derived by observation, experimentation, and rational analysis. Humanists find that science is the best method for determining this knowledge as well as for solving problems and developing beneficial technologies. "
This gets very close to scientism and does indeed cast aspersion on other means of knowing.
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Humans are an integral part of nature, the result of unguided evolutionary change. Humanists recognize nature as self-existing. "
Notice that "recognize", not "believe". That denies the validity of any viewpoint where nature requires God to exist.
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Working to benefit society maximizes individual happiness. "
This readily lends itself to misuse. Anyone remember Communism? If happiness is maximized by working to benefit society, what better than to increase everyone's happiness by requiring such work?
"Thus engaged in the flow of life, we aspire to this vision with the informed conviction that humanity has the ability to progress toward its highest ideals. "
And what happens if humanity does not "progress"? Does humanism responsibility include forcing the "progress"? Again, you can see the possibility for abuse.