Mark, you are doing a great job -- fighting the good fight -- with your clear and strong refutations, not to mention your powerful Catholic doctrinal assertions and the apologia for same.
Needless to say, with God we can do all things. Thus, I strongly encourage anyone doing battle with the heretics, witches, modernists, or whoever to fervently pray that they receive the grace necessary to open their hearts and minds to the Catholic truth.
I am reminded of how St. Joan of Arc made sure to keep out and or get rid of the "camp followers" and how she did what she could to have the men get to confession before going into battle. No doubt these actions were of no small help/significance in her gaining the "help from above" to vanquish the enemy. We don't have the physical means to get the blogging blasphemers off the Internet nor to have fellow Catholic bloggers purify their hearts, minds, and souls with a good confession, but we can certainly pray and sacrifice for those things.
As I think you know by now, I have registered on the site in question, but I am in some sort of quagmire already because the site is not allowing me to post. Rest assured I will keep trying!
Posting on these kinds of sites may not be for everyone, but if the Spirit leads you.......
and then go for it! Go for their heretical jugular! As for not having super skills in Catholic apologetics, I wouldn't be too concerned as long as you know your basic Baltimore Catechism. Keep to the basics if you have to. Don't led them run roughshod over you with all their stupid uninformed Jack Chick anti-Catholic comic book schtick.