I suspect that employers run afoul of Iowa and federal disability discrimination law more than any other type of employment discrimination law. That's partly because of the expanded focus on "perceived" or "regarded as" disability discrimination claims. Perceived or regarded as disability claims bring many more employees within the scope of disability discrimination laws than there used to be, thus increasing the number of possible legal violations by employers. But I also think that employers get themselves in trouble because, more than any other type of status that Iowa and federal employment discrimination laws establish, employers have special legal requirements regarding disabled employees or prospective disabled employees.
An example of that is the requirement of an "individualized assessment" before taking personnel action against a disabled employee, including hiring, firing, and position transfers. Employers cannot make assumptions about disabled employees, regardless of whether such employees come under the "actually disabled" category or are instead "perceived" or "regarded as" disabled. Any employment decisions made because of an employee's disability can only occur after a full review of the employee's individual circumstances, which often includes a medical analysis.
"Blanket exclusions" are a common way for employers to violate Iowa and federal disability discrimination law by making employment decisions without conducting an individual assessment of each disabled employee affected by the employer's policy. A blanket exclusion is an employer's rule, policy, or practice that excludes employees with certain disabilities from certain positions. For example, an employer may have a policy requiring a minimum level of vision for certain positions. Employees with a disability that affects their vision and fail to meet the employer's minimum vision standards have been adversely affected by the employer's blanket exclusion for people with an eye impairment.
The civil rights agencies and courts take a hard look at blanket exclusions. The determination of whether or not an employee can perform the essential functions of a particular job must be based upon an individualized assessment of the person’s ability to perform the job safely, and cannot be based simply on a blanket exclusion. The conclusion that a person poses a direct threat to the health or safety of others may not be based on generalizations or stereotypes about the effects of a particular disability; it must be based on an individual assessment. Such an individualized inquiry is essential if the law is to achieve its goal of protecting disabled individuals from discrimination based on prejudice, stereotypes, or unfounded fear. Therefore, courts give blanket exclusions the utmost scrutiny and, as a general rule, discouraged blanket exclusions.
There's one exception to the general rule against blanket exclusions. If an employer is subject to state or federal statutes or regulations that mandate or prohibit certain things among employees (for example, United States Department of Transportation regulations), the employer can legally base blanket exclusions on such statutory or regulatory requirements without committing disability discrimination. At the same time, some employers that are not subject to such statutes or regulations voluntarily adopt those requirements anyways and then try to use the statute or regulation to justify a blanket exclusion. Employers who voluntarily follow statutes or regulations that they're not required to follow and create blanket exclusions for certain disabilities as a result need to have a good reason for doing so because courts often reject an employer's attempt to justify a blanket exclusion on statutes or regulations that the employer's not bound by.