The Federal Fair Housing Act provides protection for people with physical or mental disabilities. A condominium may be viewed as a business, and therefore may also be regulated by the Americans with Disabilities Act, which also requires accessibility. Discrimination includes the refusal to make reasonable modifications to buildings that aren't currently accessible to the disabled. What appears reasonable to one person may seem unreasonable to another. That is why many discrimination issues end up being decided by the courts.
Some neighbors are concerned about secondhand smoke.
Yes - if the neighbors can convince the board of directors to approve such a restriction and if it applies to indoor spaces such as hallways or recreation rooms. If a city has not banned smoking in an outdoor park, then a court would say it's probably not reasonable. If somebody wants to smoke in a park outside, they should be able to do that. In addition, smokers can maintain their rights inside their homes. Despite problems in many associations, condominiums have done a good job of holding their value.