If a grandparent is being denied visitation rights to their grandchild, can that grandparent take the parent to court to sue for such rights?

There is such a thing as "grandparent visitation".  However, you will need the assistance of an experienced attorney.  There is case law that allows for grandparent visitation, but the it is an uphill battle and evidence must be proven in court that meets the requirements for this type of visitation.  Consult with an attorney so that you can provide the facts specific to your case.  You may contact my office and provide more detailed facts.