I certainly don't think Daksha was justified in his contempt of Shiva, or his resentment @ Shiva not bowing to him @ an earlier yagna (not showin in this serial, but I go by the original storyline, and not necessarily by what's shown).
However, I do think it was his decision as to who he wanted to invite - every host had, and has that right. Shiva too agreed, and in fact pointed out to Sati that they were not invited to the yagna, and therefore, it would be improper of either of them to go. Sati too regretted insisting on coming after she realized that the slight was deliberate, but at this point, she felt like she had to avenge the insult to the both of them, and so decided to end her life so that she wouldn't have to live on as his daughter.
I do think Daksha could have more gracefully handled it by telling Sati that he chose not to invite them for reasons he didn't wish to share. Or b4 the yagna, send a message to Shiva and Sati telling them that he was hosting a yagna, and that they were not invited. But my point was that he did have a right not to invite them: insulting them however, was what was crossing the line.