One of the things that one finds quite often among Middle Easterners, South Asians, and East Asians (collectively as Asians) is that there is a very strong expectation that it is only desirable if you date within your own ethnic group. If the family of such a person finds out that he is going out with someone of a different ethnicity, they will likely grill him/her endlessly about whether or not he/she is loyal to their heritage, if the significant other is trying to take advantage of him/her, whether or not he/she “really cares” about how the family feels, etc. Unfortunately, many friends and extended family members serve as an extended set of informers for the central family, so your boyfriend may be hesitant of introducing you to said individuals. The atmosphere is very hostile and he is likely trying to protect both you and himself from this blowout until the relationship has passed the point of no-return.
The only exception to this rule that I have found is when such individuals “date White”, which is, in many Asian minds, to be “marrying up” and there are fewer issues with such relationships, but this can differ between Asian families
In many ways, this is a form of racism which should be pointed out and discussed. If you find this treatment offensive, you should talk about it with your boyfriend and make it clear how you feel.