Yes, more countries should write laws to block Islam from becoming their official religion. However, this assertion needs to be delivered with a caveat: All religions should be banned from becoming the state religion of any country. Governments should be completely secular and the governing of countries should be based in fact, not fantasy.
Countries should offer their citizens freedom of religion, and go one step further than Slovakia by abolishing the idea of a state religion altoghther. It is not Islam itself that is the problem, it is the fact that countries have become more diverse than they ever have been before and legislating morality is no longer a good idea.
Slovakia's law isn't any different than the law that the United States has had since its inception. That law is for the separation of church and state. Many Islamic religious groups want to see Islam instated as the state religion. The next step is to impose their practices on the people. Slovakia said no before that could happen.
It's nice for places to not have Islam as the official religion, but realistically no country should have an official religion. Once you mix religion and politics, you get sub-optimal results based on the inherent insanity of religion. When you're working with real people for real political gains, you shouldn't have tenets of religion involved screwing everything up.