My late teacher's journey through Aikido and life (read as the same - Shugyo) was a spiritual one. That was personal to him and those that wished to follow the spiritual side did so as a personal path also.
I would never force spiritual teachings on anyone. That is there choice! Encourage students to read about Aikido, all the way back to it's origins in the 8th century. If they find their way includes a spiritual side, then that is their choice.
Aikido can be practiced as a purely physical activity. If fact, the problem is not those who practice Aikido purely physical, but the problem is those who practice Aikido purely spiritual!!!!