The reason we say homeopathy is implausible is because we have a great deal of evidence to the contrary -- as you say, not clinical trials, but laws of physics

The reason we say homeopathy is implausible is because we have a great deal of evidence to the contrary -- as you say, not clinical trials, but laws of physics that are very well understood and that are completely incompatible with homeopathy. The very idea of plausibility must always go back to evidence; otherwise it's merely wishful thinking.