Is it true that educational videos can harm children?

No. Education of our children formal and informal is best provided first by a trusted adult, usually the caregiver. This format is personal and allows for honing the child's interpersonal skills. This said, a supervised use of educational vidoes, allows for discussions of any questions and clarification of some of the contents can prove very useful. The videos cannot be used as techno nannies.
No. The current recommendations are for no television watching before the age of 2 years old. This sometimes becomes inevitable when there are multiple children in the household, or when any family member wants to watch television. I recommend to not use the tv as a babysitter at any age, parental prescreening when possible, limited tv watching and discussion with your kids. Make it interactive.