Is it ok to break a religious rule if it would offend someone (to Jews primarily)?

All are welcome to answer (except dismissive atheists whose 2 cents I don't care for) but this scenario involves a Jewish situation - if someone keeps kosher dietary laws and goes to eat at another Jew's home who serves something that isn't marked with the kosher symbol on the box but he goes over all the ingredients and there is no meat/dairy mixture so he says it's ok to eat, should the strict kosher observer eat it to avoid offending the other one or turn down the meal completely and let the other Jew eat alone and say it's not kosher enough for their standard?