At this moment I can suggest that you hide or disable the slider (when minValue is equal to maxValue) .
When we considered slider behavior, we decided to forbid this particular case. However, this issue has now been logged for reconsideration and future implementation.
To create a better RadSlider control we will appreciate your feedback on this issue. What in your opinion must happen when RadSlider is with minValue = maxValue?
Thanks for your vcaluable feedback.
All the best,
the Telerik team