There are several things about the Marigold/Hanners shipping trend that weird me out, and a few things that piss me off. I'll start with what pisses me off: the fact that both Hanners and Marigold were for no apparent reason assumed to be gay. The reasons they were assumed to be gay were borne of sexist and homophobic reasoning and stereotyping respectively (that is to say, Hanners of sexist reasoning and Marigold of homophobic stereotyping). People look at Hannelore, and because she's not constantly hitting on/flirting with/having wild rampant sex with any male members of the cast, and because she has reacted negatively to physical interactions with (coincidentally) only male characters, it's assumed that she must like girls instead. While all conventional reasoning, combined with her brief history of displaying that she is in fact very sexually attracted to men, points to her severe OCD as the culprit, we instead opt to believe that she must be a lesbian because somehow, in our subconscious minds, we are incapable of seeing women outside of a sexual context or in any context which may, itself, put them beyond the bounds of sexuality. With Marigold, on the other hand, it's the opposite. Marigold, right from her introduction, was shown as being unhygenic, slovenly and abrasive. In other words: not ladylike. And, as the stereotype goes, effeminate men are gay, and uncouth women are lesbians. And what pisses me off was that apparently in the minds of many (not just the shippers), her demeanor was more of an indication of her sexuality than the fact that she thoroughly enjoys man-on-man.
The other aspect of it is how it was almost just assumed from the second that they started hanging out that they had to be romantically involved. I may be being overly analytical here, but I believe that this in itself also stems from some inborn conception we have of women as purely sexual beings. While no one seems to challenge the assessment that Marten and Steve or Wil and Sven are purely friends, the first (second, but I'll get to that) female-to-female friendship instantly earns thoughts that they must be attracted to each other (the real first being Dora and Faye, with it being repeatedly established that Dora actually is attracted to Faye, just not beyond physically).
So in short (for once from me...), the reason I take issue with HannelorexMarigold is because I feel it's not just an issue of thinking they'd be cute/hot together, it's from the unsubstantiated idea we have that it could actually happen, and the reasoning we use to get there. Notice that I say we because I don't mean exclusively the shippers (nor do I mean everybody, or even necessarily most people).