What is the basis of the prohibition for an observant Jew from going to a Hindu Temple, or attending a Diwali Party?
Is there no exception for work related or social/neighborly visits, which lack any intent to worship another diety?
What is the basis of the prohibition for an observant Jew from going to a Hindu Temple, or attending a Diwali Party?Broadly, Observant Jews don't go to others' houses of worship period, even during non festival days. The same applies to non house of worship parties/celebrations where other gods are involved.
There are several ideas behind the prohibition. A few are...
"appearances" - What would a an Observant Jew think seeing another Observant Jew go into another's house of worship? This is a big deal and raises many questions and concerns.
"difficulties" - Should an Observant Jew enter another house of worship or even an offsite Diwali party, there are a number of difficulties unknown to the others that may cause conflict or friction. Not being able to eat or drink their celebratory food/drink, not shaking hands with the opposite gender, immodestly dressed women, images/idols of other gods in a home, etc, etc.
"temptation" - A warm and celebratory atmosphere, with delicious food and drink, served by a beautiful hostess are strong temptations, better to never put yourself in that position.
Is there no exception for work related or social/neighborly visits, which lack any intent to worship another diety?Generally, no, for reasons above. Work-related issues, especially when supporting a family, can have some leniencies.
How is Ivanka different? First, everyone knows - in advance - why she is going, there is no question or uncertainty. Second, it is very public. Third, she is surrounded by people who plan in advance to avoid "difficulties" and control "appearances."
Lastly, her appearance is an opportunity for a tremendous mitzvah.