Agreed, though I'll give us a B- on the "accepting diversity" front.I mirror what others said above, that in general in engineering if you have the skills to get the job done, you're accepted into the community. I give engineering an A for accepting diversity in that respect. But as far as actually being diverse, I think we're more like a D (but not for a lack of trying.)
I think it has less to do with the profession itself - I don't think the profession cares for the most part, there are just too many contributing factors at the pre-collegiate level that influence the overall makeup. Excluding those that have "the knack" (and there are plenty of engineers who don't), I think most of it comes down to poor education at the K-12 level and lack of understanding and difficulty of getting the financial assistance needed to enroll in college, and that comes down to socioeconomic status, which has a strong correlation with race in many (most?) parts of the country.
I'm basing the above comments on American-born population - I think there IS segregation in the industry at the managerial level, but from what I've seen, I think that's attributed more towards a combination of how academics are handled internationally vs. in the states, and the economic status of the country of origin. I do think US colleges focus more on collaborative efforts/personal interaction than schools from India and China as an example, and when coupled with language barriers, the people with better verbal communication and interpersonal skills gets the promotion, placing the foreign-born workers at an inherent disadvantage. In respect to overall hiring practices, I think there are also many volume-based engineering firms that know they can hire foreign Engineers on the cheap, with little to no intent to ever promote or offer them professional development opportunities.
I do know of one manager who is of Asian decent (I'm not sure exactly which country), has a thick accent, but is a nice, intelligent guy. The company has no problem sending him to ASME meetings, etc. on his own to try and pitch work/build relationships, but when they go to some of the operating plants to try and do the same (e.g. WV/PA area), the company sends the slick-talkin' good ol' boy along with him to try to make the sale. Shit like that is why I can't give the industry an A - I can't fault the company for recognizing the bias and adjusting for it, but the fact that they know up front that their clients across the country have various inherent prejudices says quite a bit about the profession.