Your question is a re-occuring one because everyone's opinion is different. I think the dangers of steam are for pieces that are already cut out; i.e., using steam might warp the fabric so a 4x4 block might end up a 4.1 block. This is especially true for pieces with bias edges such as triangles. Also, for cut pieces, don't iron back & forth, always go up & down. This is true for ironing seams, also.
But, for fabric which hasn't been cut for a pattern, I use a spray bottle of water, lightly spritz, and iron away.