What do I do if I realize that my host’s kashrus standards are not up to my own?
Those with high kashrus standards must sometimes choose between offending their host and compromising their principles.
It should be noted that stating the issues—what on the menu they feel comfortable eating, and what they don’t—in a polite, mentchliche (sensitive) manner will often go over without the host being offended.
However, in an uncomfortable situation, one may be lenient and use utensils that came in contact with food that one avoids due to a chumrah (stringency). Similarly, if necessary, one may eat food that is mutar b’dieved (permitted after the fact), which they don’t usually eat. Obviously, none of this applies if the food is assur min hadin (inherently forbidden).
On their part, hosts should be sensitive to their guest’s needs and refrain from serving food that is not up to their guest’s kashrus standards. This is actually a halachic requirement, and not merely proper etiquette.