While extremely presumptuous of Martha to invite Lois' parents to dinner, she also felt the younger couple might need someone to run interference for them. Learning of Robin's existence and being thrust into instant parenthood was enough for anyone to handle. They certainly didn't need an overbearing mother breaking their spirits as well.
I think Martha did wrong for several reasons. First, it was up to Lois to decide when to tell *her* parents. Lois being Lois, I expected her to get mad at Martha - and I would totally agree with her. Martha treated Lois and Clark like children, not grown-ups.
Second, knowing Ellen it is easy to guess what her reaction would be. It was totally irresponsible from Martha towads Robin to arrange so that the little boy heard Ellen's first reactions.
Instead, it would be best to Lois to tell Ellen and only after she would have make a promise to behave, let her meet Robin. I guess Lois would have maybe wanted to spare also Clark's feelings and tell her mom alone.
I have begun to suspect that underneath, Robin has some serious problems. Every time when there is a problem, he withdraws. He can't bear that somebody doesn't like him straightaway.
I hope that Lois and Clark teach him *soon* that in the situation like these, he could talk with them and invent a way to deal with such persons.
Maybe he could need to be a part in a baseball team where you don't have to *like* everyone, only get along with all.