The problem with dismissing what a future OB has to say about breastfeeding (or any HCP for that matter) -- is that while some people are comfortable ignoring advice from their doctors, and researching and making their own decisions - there are a LOT of people who will take what the Doctor says as absolute truth.

So an OB who thinks women shouldn't bf beyond a year, may compromise many bf relationships.
*Is s/he going to be supportive to a mother who is dealing with mastitis at 6 months, or is s/he going to say, "Oh, you're halfway there, it's OK to stop."
*Is s/he going to tell a mom who finds herself pregnant while still bf her child (whether said child is 10 months or 22 months) "You must wean immediately, your milk has no value for the child anyway at this point."
*Is s/he going to tell the mother to wean when she comes in for her annual check-up (about a year after birth), with similar patronizing and inaccurate comments about the WHO recommendations?
....
There are lots of times when the OB is the one the breastfeeding mother is talking to. My OB has been *wonderful* about me breastfeeding, and really supportive. It probably wouldn't have changed my decisions anyway, but there's a lot to be said for having an OB say to a mother:
*Well, of course you're making enough milk. We'll get this figured out. Are you seeing an LC (who are you working with)?
*Still breastfeeding after a year? That's great.
*[After a miscarriage] - Make sure your dd keeps nursing, that will help.
*When I let him know I was back on my Elimination Diet in hopes we don't deal with allergies with this incoming arrival, says, "Great mom!" instead of urging me to ff instead.
*Most recently (yesterday's 37 week appointment): "Is baby going to live with you and dh, or in a crib?" (and when told "with us," responds with a big thumbs-up and "That's great, it's what works best."

I loved the "live with us" comment. What a description!
He's definitely pro-bf and while he's not always 100% informed (he's not an LC, after all) -- I think for any clients who are planning on bf, he's really supportive. It's nice to be able to tell the IL's that the OB and the Ped both agree about a treatment course (whether it's mastitis or allergies or etc.). It's nice to know that they don't think I'm a wacko. And, I do think that for mothers who are less informed and less supported in their breastfeeding, it could make or break a bf relationship.
I guess my hope/thought is that if the OP is able to address this again with the resident in question, he may come 'round to being more informed, more accepting, and possibly in a few years - an actual bf supporter. It's worth a shot, I think.