As an uncompromising vegan myself, the only reason why I would personally even consider buying meat is if it is for someone else. Indeed, this issue comes up more often than I'd care, as my girlfriend, who is vegetarian (she eats eggs), ironically likes to cook and prepare meals including meat dishes for visiting non-vegetarian family and friends. They're not going to be pleased to come if we offer them mung bean sprouts and rice noodles for dinner, so I can certainly understand why one might buy meat in a situation like that.
Is it ethical? In the long run, it seems to me six of one, half dozen another in the case of entertaining guests. They're going to eat it regardless of what you serve, and might stop visiting for dinner if you refuse to prepare or provide meat dishes for them... meaning, going forward, they'd probably be eating meat on nights when you'd have had them over. At least if you buy it yourself, you could even ensure it's organic meat, so at least the animals did not suffer while they were alive.