mdd: Do you consider it okay to consider one skin color more desirable than another for shidduchim? Speaking personally, would you be less comfortable marrying (or having your son marry) a black girl?
Do you consider it okay to consider being a born-Jew more desirable than a ger for shidduchim? You said yichus is a valid positive consideration, and virtually every born Jew (especially coming from a frum line) has better yichus than geirim. If someone feels he will only marry someone with a lot of good yichus (which you appear okay with), he is effectively excluding geirim in his shidduchim.