Not always bad for us on the retail end, until you are fully invested in a position. Then, it kinda sucks and wears on your patience for the thing to go up.
I also think alot us us who play with pennies are kinda jealous of the MMs because we can't short pennies but they can (in the name of an 'orderly market', whatever that means). We can watch it go down, know it's going down further (can actually make it go down ourselves with just a few shares), and can't benefit from what we suspect.
MMs, on the other hand, can sell shares they don't own to lemmings like me and you who follow news and do a little DD, then turn around and whack away at the bid to cause a panic sell-off. They then just sit there in the current and suck up plankton like baleen whales.
Long story short, MM short selling can make you buy high and sell low if you don't have the patience of Job.