Kelly, I don't have any idea who would send such a tasteless and unfriendly e-mail to you.
Whatever you do, don't put any stock in it, and don't let it get you down. Remember this is your journal. Not anyone else's. It's yours, and yours alone. The fact that you allow others to read it is a privilege, and nothing more.
You have the right to put anything and everything that you want in your journal, and you have the right to completely ignore everyone else. Anyone who complains about what someone else puts in their own journal, or tries to tell other people what to write in their journal, is showing a level of conceit that borders on the incredulous.
What gives anyone else the right to even think they should control your journal? This is a journal by you, for you, and about your life. If you wish to speak of your child, which I personally enjoy reading about, then by all means, keep doing so. That is, after all, why you are keeping a journal. ;-)